Deserter of an art form (3)
I believe the answer is:
rat
'deserter' is the definition.
(thesaurus)
'an art form' is the wordplay.
'form' indicates an anagram.
'art' is an anagram of 'RAT'.
'of' acts as a link.
(Other definitions for rat that I've seen before include "Grass" , "Abandon" , "Tell-tale" , "Sewer rodent" , "that gets out of stricken vessel" .)