Part of FBI agents in place (7)
I believe the answer is:
segment
'part' is the definition.
(segmenting is a kind of parting)
'fbi agents in place' is the wordplay.
'fbi agents' becomes 'g-men' ('G-man' can be a synonym of 'fbi agent').
'in' is an insertion indicator.
'place' becomes 'set' (synonyms).
'gmen' placed inside 'set' is 'SEGMENT'.
'of' acts as a link.
(Other definitions for segment that I've seen before include "Portion" , "Gets men with part cut off" , "One part of a whole" , "Part of citrus fruit" , "(Divided-up) part" .)