Man soon set to build -- builder! (10)
I believe the answer is:
stonemason
'builder' is the definition.
(thesaurus)
'man soon set to build' is the wordplay.
'to build' indicates anagramming the letters.
'man'+'soon'+'set'='mansoonset'
'mansoonset' is an anagram of 'STONEMASON'.
(Other definitions for stonemason that I've seen before include "Building worker" , "Man's on toes (anag) - craftsman" , "Architectural carver" , "Monumental worker" , "Rock craftsman" .)