Extra small cut (5)
I believe the answer is:
spare
'extra' is the definition.
('spare' can be a synonym of 'extra')
'small cut' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'cut' becomes 'pare' (I've seen this before).
's'+'pare'='SPARE'
(Other definitions for spare that I've seen before include "Not required" , "Extra item just in case" , "Thin; surplus" , "Thin; left over" , "This tyre around the middle is fat" .)