Surrealist backed enthralling Republican (6)
I believe the answer is:
breton
'surrealist' is the definition.
(co-founder of the surrealist movement)
'backed enthralling republican' is the wordplay.
'backed' becomes 'bet on' (to bet on is to back or support).
'enthralling' indicates putting letters inside.
'republican' becomes 'r' (abbreviation).
'beton' placed around 'r' is 'BRETON'.
(Other definitions for breton that I've seen before include "One from Brest" , "A native of Brittany, France" , "Surrealist" , "Cooked with cheese and/or breadcrumbs on top" , "French language class" .)