Böcek kovucu çadır tentesinin altında kaldı.

Literally:

• böcek = bug / insect
• kovucu = something that drives away / repels

So böcek kovucu means bug repellent / insect repellent.

It comes from the verb kovmak, which means to chase away or drive away.

The ending -ucu / -ücü often makes a word meaning something or someone that does that action. So:

• kovmak = to drive away
• kovucu = repellent / thing that drives away

So böcek kovucu is literally bug-driver-away.

Here it works as a noun phrase: it names a thing, namely insect repellent.

But structurally, kovucu can also behave like an adjective. For example:

• böcek kovucu sprey = insect-repellent spray

So Turkish lets this kind of word act flexibly depending on context.

Because çadır tentesi is an indefinite noun compound, which is a very common Turkish structure.

It works like this:

• çadır = tent
• tente-si = its canopy/awning

Together, çadır tentesi means tent canopy / tent fly / tent awning as a set expression or type of thing.

By contrast, çadırın tentesi is a more explicit possessive phrase meaning something like the canopy of the tent or this tent’s canopy.

So:

• çadır tentesi = tent canopy, tent fly
• çadırın tentesi = the tent’s canopy

Because the phrase is followed by altında, and Turkish normally says X-in altında for under X.

So the noun phrase has to go into the genitive form:

• çadır tentesi = tent canopy
• çadır tentesi-nin = of the tent canopy

That is why you get:

• çadır tentesinin altında = under the tent canopy

altında means under it / beneath it.

It is built from:

• alt = lower part, underside, below
• -ı = possessive ending
• -nda = locative ending, meaning in/on/at

So altında is literally something like at its underside or under it.

This is a very common Turkish pattern:

• masanın altında = under the table
• köprünün altında = under the bridge
• çadır tentesinin altında = under the tent canopy

kaldı is the past tense of kalmak.

Depending on context, kalmak can mean:

• stay
• remain
• be left
• end up staying

In this sentence, kaldı suggests that the insect repellent remained there or got left there.

So the English meaning may be:

• stayed under the tent canopy
• remained under the tent canopy
• was left under the tent canopy

Because it is the subject of the sentence.

The verb kalmak is intransitive, so it does not take a direct object here. The thing that remained/stayed is böcek kovucu, so it stays in its basic dictionary form.

Very roughly, the structure is:

• böcek kovucu = subject
• çadır tentesinin altında = location
• kaldı = verb

Because Turkish normally puts the finite verb at the end of the sentence.

A neutral word order here is:

• Subject + location + verb

So:

• Böcek kovucu
  • çadır tentesinin altında
    • kaldı

You can move parts around for emphasis, but kaldı will very often stay at the end:

• Çadır tentesinin altında böcek kovucu kaldı.

That sounds more marked or emphasis-driven, but it is still grammatical.

Turkish has no articles like a/an/the.

So the sentence itself does not force one choice. English has to supply it from context.

Depending on the situation, this could be:

• The insect repellent stayed under the tent canopy.
• An insect repellent stayed under the tent canopy.
• The bug spray was left under the tent fly.

In real use, if both speakers already know which repellent they mean, English will usually use the.