Clue: Bear – one sits regularly for surrealist (5)
Answer: ERNST
Explanation: Bear – one sits regularly for surrealist (5)
(b)**E**(a)**R**(o)**N**(e)**S**(i)**T**(s) [*regularly*] 
*Refers to Max Ernst (1890-1976), a German poet and artist who was involved in the establishment of the Dada movement.