Doctor lent a coat to artist (9)
I believe the answer is:
canaletto
'artist' is the definition.
(I've seen this before)
'doctor lent a coat' is the wordplay.
'doctor' indicates an anagram.
'lent'+'a'+'coat'='lentacoat'
'lentacoat' is an anagram of 'CANALETTO'.
'to' acts as a link.
(Other definitions for canaletto that I've seen before include "Master of the canvas" , "old master?" , "Eighteenth century artist associated with Venice" , "C 18 Italian artist" , "Italian painter known for his scenes of Venice, d. 1768" .)