Unsuitable kind of paint (5)
I believe the answer is:
inapt
'unsuitable' is the definition.
(thesaurus)
'kind of paint' is the wordplay.
'kind of' indicates anagramming the letters.
'paint' anagrammed gives 'INAPT'.
(Other definitions for inapt that I've seen before include "not fit for purpose" , "Ill-suited" , "Free from deceit" , "Cartoon duck" , "Unsuited" .)