Painter of a human extraterrestrial (5)
I believe the answer is:
manet
'painter' is the definition.
(thesaurus)
'a human extraterrestrial' is the wordplay.
'a human' becomes 'man' (man is a kind of human**).
'extraterrestrial' becomes 'et' (I've seen this in other clues).
'man'+'et'='MANET'
'of' is the link.
(Other definitions for manet that I've seen before include "artistic individual" , "French painter" , "Edouard ___, painted Dejeuner sur l'herbe, d. 1883" , "Olympia artist" , "Painter of Le Dejeuner sur l'herbe, d. 1883" .)