After reflection, headquarters provided understanding religious law (4)
I believe the answer is:
fiqh
'understanding religious law' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'after reflection headquarters provided' is the wordplay.
'after reflection' says the letters should be written backwards.
'headquarters' becomes 'HQ' (synonyms).
'provided' becomes 'if' (eg 'provided it's sunny' means 'if it's sunny').
'hq'+'if'='hqif'
'hqif' written backwards gives 'FIQH'.
Can you help me to learn more?
(Another definition for fiqh that I've seen is " study of religious law".)