Hammer in part of building work (6)
I believe the answer is:
wallop
'hammer' is the definition.
(thesaurus)
'part of building work' is the wordplay.
'part of building' becomes 'wall' ('wall' is part of 'building').
'work' becomes 'op' (abbreviation for opus).
'wall'+'op'='WALLOP'
'in' acts as a link.
(Other definitions for wallop that I've seen before include "A heavy resounding blow (6)" , "batter" , "Best" , "Beat" , "Punch" .)