Wearing down, turning it into art (9)
I believe the answer is:
attrition
'wearing down' is the definition.
(thesaurus)
'turning it into art' is the wordplay.
'turning' indicates an anagram.
'it'+'into'+'art'='itintoart'
'itintoart' is an anagram of 'ATTRITION'.
(Other definitions for attrition that I've seen before include "Process of gradually wearing down" , "Wearing down of enemy" , "Grinding down" , "Wearing down - natural wastage" , "gradual loss of souls?" .)