Working with DIY turns nasty (8)
I believe the answer is:
industry
'working' is the definition.
(being industrious or hard-working)
'with diy turns nasty' is the wordplay.
'with' means one lot of letters go next to another.
'nasty' is an anagram indicator.
'diy'+'turns' is 'diyturns'.
'diyturns' is an anagram of 'INDUSTRY'.
(Other definitions for industry that I've seen before include "Craft" , "Branch of trade" , "Commerce" , "Diligence" , "The manufacture or production of goods" .)