The butchers out to become a composer (8)
I believe the answer is:
schubert
'a composer' is the definition.
(Franz Schubert, 1797-1828)
'the butchers out' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'butchers' is an anagram of 'SCHUBERT'.
'to become' is the link.
(Other definitions for schubert that I've seen before include "Lieder composer" , "Austrian composer, d. 1828" , "Austrian composer of the Trout piano quintet" , "Franz -, Austrian composer (Trout Quintet, etc)" , "Butchers embrace great German composer" .)