Compare some of Monet's art? No chance, on reflection (8)
I believe the answer is:
contrast
'compare' is the definition.
(I've seen this before)
'some of monet's art? no chance on reflection' is the wordplay.
'some of' indicates a hidden word.
'on reflection' shows that the letters should be reversed in order.
'tsartnoc' is hidden within 'monets art no chance'.
'tsartnoc' backwards is 'CONTRAST'.
(Other definitions for contrast that I've seen before include "Differ strikingly" , "Degree of difference found on tracts" , "No tracts by way of difference" , "Distinction" , "Dissimilarity of things compared" .)