Because in this sentence duidelik comes after the verb is, so it is a predicate adjective. In Afrikaans, predicate adjectives usually stay in their basic form.
So:
The adjective does not change for gender or number.
No, not in the way English learners may expect from languages like German or Dutch. Afrikaans does not use grammatical gender in its articles the way those languages do.
So die is used regardless of whether the noun would historically have been masculine, feminine, or plural.
That makes Afrikaans simpler here:
Grammatically, yes: 'n rigting is duidelik means a direction is clear.
But the meaning changes:
So the original sentence points to a particular direction, not just any direction.
A rough English-friendly pronunciation is:
RIKH-ting
A few notes:
If you cannot make the Afrikaans g sound yet, using a sound like the ch in Scottish loch is a decent approximation.
A rough approximation is:
DOY-də-lək
The difficult part is ui, which is a characteristic Afrikaans vowel sound. English does not have an exact equivalent. For beginners, something between day and boy can help as an approximation, but it is not exact.
Also:
Yes, several useful ones:
Basic present tense of to be
No adjective agreement here
Simple statement word order
So even though the sentence is short, it is a very good model for basic Afrikaans sentence structure.