Learn Farsi: این مورد جدا است.

The core meaning of the noun مورد is "instance", "item", or "case". When you use the common phrase در مورد, you are literally saying "in the case of" or "in the instance of", which translates smoothly to "about". In this sentence, این مورد simply means "this specific instance" or "this case".

How would this sentence be pronounced in everyday conversational Farsi?

In spoken Farsi, the verb است (is) attaches to the previous word. Because جدا ends in a long vowel (â), it merges with است to form جداست (jodâst). So you will almost always hear it spoken as این مورد جداست.

Does جدا only mean the adjective "separate", or can it be used as an adverb too?

It can be used as both! Here it acts as an adjective, but it is also commonly used as an adverb meaning "separately" or "apart". As a bonus tip for everyday conversation, if you say جدا with a questioning tone, it means "Really?!" or "Seriously?!".