Butcher's good weapon (6)
I believe the answer is:
glance
'butcher's' is the definition.
(I've seen this before)
'good weapon' is the wordplay.
'good' becomes 'g' (abbreviation).
'weapon' becomes 'lance' (lance is a kind of weapon).
'g'+'lance'='GLANCE'
(Other definitions for glance that I've seen before include "Momentary look" , "it has a metallic lustre" , "Oblique impact" , "Look quickly at -- cricket stroke" , "Batsman's stroke" .)