I see men fighting opponents (7)
I believe the answer is:
enemies
'opponents' is the definition.
(I know this)
'i see men fighting' is the wordplay.
'fighting' indicates an anagram (I've seen this in other clues).
'i'+'see'+'men'='iseemen'
'iseemen' anagrammed gives 'ENEMIES'.
(Other definitions for enemies that I've seen before include "Those we fight" , "Foes, adversaries" , "Foes, opponents" , "Foes, hostile groups" .)