Relative to artist, returning unsure (7)
I believe the answer is:
unclear
'unsure' is the definition.
(thesaurus)
'relative to artist returning' is the wordplay.
'relative' becomes 'uncle' (uncle is a kind of relative).
'to artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'returning' shows that the letters should be reversed in order.
'ra' reversed gives 'ar'.
'uncle'+'ar'='UNCLEAR'
(Other definitions for unclear that I've seen before include "Not distinct in nuclear way" , "Not transparent or free from doubt" , "hard to understand" , "Indistinct" , "Not easy to see or understand" .)