Expertise shown by butcher on board (6)
I believe the answer is:
skills
'expertise' is the definition.
'butcher on board' is the wordplay.
'butcher' becomes 'kill'.
'on' means one lot of letters goes inside another.
'board' becomes 'ss' (I've seen this in other clues).
'kill' inserted inside 'ss' is 'SKILLS'.
'shown by' acts as a link.
(Other definitions for skills that I've seen before include "Working abilities acquired through practice and training" , "Areas of expertise" , "facilities" , "Special aptitudes or abilities" , "Abilities to do things well" .)