Look for a key-cutter (6)
I believe the answer is:
glance
'look' is the definition.
(I know that glance is a type of look)
'key-cutter' is the wordplay.
'key' becomes 'g' (musical key).
'cutter' becomes 'lance' (lance is a kind of cutter).
'g'+'lance'='GLANCE'
'for a' acts as a link.
(Other definitions for glance that I've seen before include "Look briefly or bounce off" , "Momentary look" , "batsman's shot" , "Butcher" , "Batsman's stroke" .)