Officer material, leading soldier perhaps (8)
I believe the answer is:
sergeant
'officer' is the definition.
(I've seen this before)
'material leading soldier perhaps' is the wordplay.
'material' becomes 'serge' (serge is a kind of material).
'leading' means one lot of letters go next to another.
'soldier perhaps' becomes 'ant' (soldier is a type of ant).
'serge'+'ant'='SERGEANT'
(Other definitions for sergeant that I've seen before include "Rank above corporal" , "CARRY ON FILM" , "Military or police officer" , "Reagents (anag)" , "Noncommissioned military officer" .)