The most common and most likely answer to this crossword clue is the 5 letter word TALAQ
T
A
L
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Q
Buddy explains!

The straight part
We know that "form of Islamic divorce" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case form of islamic divorce = talaq.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does TALAQ mean?
TALAQ noun- An Islamic divorce, sanctioned by the Qur'an.
- To divorce somebody by this means.