Division having FBI agents positioned outside (7)
I believe the answer is:
segment
'division' is the definition.
(I've seen this before)
'fbi agents positioned outside' is the wordplay.
'fbi agents' becomes 'g-men' ('G-man' can be a synonym of 'fbi agent').
'positioned' becomes 'set' (I am not sure about this - if you are sure you should believe this answer much more).
'outside' means one lot of letters goes inside another.
'gmen' put inside 'set' is 'SEGMENT'.
'having' acts as a link.
Can you help me to learn more?
(Other definitions for segment that I've seen before include "Portion" , "One part of a whole" , "(Divided-up) part" , "Part of citrus fruit" , "One of several parts of a whole" .)