Transformation of construction firm -- hurt's been nasty (13)
I believe the answer is:
refurbishment
'transformation of construction' is the definition.
'firm hurt's been nasty' is the wordplay.
'nasty' indicates anagramming the letters.
'firm'+'hurts'+'been'='firmhurtsbeen'
'firmhurtsbeen' with letters rearranged gives 'REFURBISHMENT'.
(Other definitions for refurbishment that I've seen before include "Doing-up" , "Clean-up" , "Thorough change of decor etc" , "Renovation" .)