Arm is small, and nose (7)
I believe the answer is:
shooter
'arm' is the definition.
(I've seen this before)
'small and nose' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'and' is a charade indicator (letters next to each other).
'nose' becomes 'hooter' (hooter can informally mean someone's nose).
's'+'hooter'='SHOOTER'
'is' acts as a link.
(Other definitions for shooter that I've seen before include "Gun (sl.)" , "photographer?" , "aiming to score goal?" , "small arm?" , "Gun user" .)