Naked belligerence ultimately shown by retired debt-collector (4)
I believe the answer is:
nude
'naked' is the definition.
(I've seen this before)
'belligerence ultimately shown by retired debt-collector' is the wordplay.
'ultimately' suggests the final letters.
'shown by' means one lot of letters go next to another.
'retired' shows that the letters should be reversed in order.
'debt collector' becomes 'dun' (I've seen this in other clues).
The final letter of 'belligerence' is 'e'.
'dun' backwards is 'nud'.
'e' put after 'nud' is 'NUDE'.
(Other definitions for nude that I've seen before include "revealing all" , "Unclad" , "Not dressed" , "not in gear" , "Undraped figure" .)