One working on buildings — top of skyscraper next? (6)
I believe the answer is:
slater
'one working on buildings' is the definition.
(slaters work on roofs)
'top of skyscraper next?' is the wordplay.
'top of' indicates taking the first letters.
'next?' becomes 'later' (I've seen this in other clues).
The initial letter of 'skyscraper' is 's'.
's'+'later'='SLATER'
(Other definitions for slater that I've seen before include "Does one abuse" , "Craftsman" , "Man on top" , "Professional roof worker" , "High-reaching worker perhaps" .)