Extra quarter to trim off (5)
I believe the answer is:
spare
'extra' is the definition.
(both can mean left over)
'quarter to trim off' is the wordplay.
'quarter' becomes 's'.
'to trim off' becomes 'pare' (I've seen this in another clue).
's'+'pare'='SPARE'
(Other definitions for spare that I've seen before include "Refrain from using" , "Thin; elegantly simple" , "Superfluous" , "Don't use" , "Lean and treat mercifully" .)