Group has FBI agents placed outside (7)
I believe the answer is:
segment
'group has' is the definition.
'segment' can be an answer for 'group' (thesaurus). I'm unsure of the 'has' bit.
'fbi agents placed outside' is the wordplay.
'fbi agents' becomes 'g-men' ('G-man' can be a synonym of 'fbi agent').
'placed' becomes 'set' (synonyms).
'outside' is an insertion indicator (some letters go outside others).
'gmen' placed within 'set' is 'SEGMENT'.
Can you help me to learn more?
(Other definitions for segment that I've seen before include "Division" , "Part of citrus fruit" , "Part of, eg, an orange" , "Portion" , "Piece of an orange" .)