Left it — involving artist for painting (8)
I believe the answer is:
portrait
'painting' is the definition.
(portrait is a kind of painting)
'left it involving artist' is the wordplay.
'left' becomes 'port' (left side of a ship - opposite of starboard).
'involving' is an insertion indicator.
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'port'+'it'='portit'
'portit' going around 'ra' is 'PORTRAIT'.
'for' acts as a link.
(Other definitions for portrait that I've seen before include "Painting of a real person" , "Person's picture" , "Oil perhaps" , "(Person's) painting" , "Picture of person" .)