Paint may be unsuitable (5)
I believe the answer is:
inapt
'unsuitable' is the definition.
(I've seen this before)
'paint may be' is the wordplay.
'may be' is an anagram indicator.
'paint' is an anagram of 'INAPT'.
(Other definitions for inapt that I've seen before include "not seemly" , "not fit for purpose" , "Unsuited" , "Unsuitable - paint (anag)" , "Not suitable or appropriate" .)