Alas I’m no fancy oil painting (4,4)
I believe the answer is:
mona lisa
'oil painting' is the definition.
(painting by Leonardo da Vinci)
'alas i'm no fancy' is the wordplay.
'fancy' is an anagram indicator.
'alas'+'im'+'no'='alasimno'
'alasimno' with letters rearranged gives 'MONA LISA'.
(Other definitions for mona lisa that I've seen before include "Mysterious-smile Louvre portrait" , "depicted, in the Louvre" , "Da Vinci painting" , "Famous painting of enigmatic woman by daVinci" , "Louvre painting" .)