Before English period, inspectors withdraw (9)
I believe the answer is:
disengage
'withdraw' is the definition.
(synonyms)
'before english period inspectors' is the wordplay.
'before' is a charade indicator (letters next to each other).
'english' becomes 'eng'.
'period' becomes 'age' (age is a kind of period).
'inspectors' becomes 'dis' (DIs, detective inspectors).
'eng'+'age'='engage'
'engage' put after 'dis' is 'DISENGAGE'.
(Other definitions for disengage that I've seen before include "free" , "Withdraw" , "Separate, release, detach" , "Remove (troops) from a conflict" .)