Tolerate a beast (4)
I believe the answer is:
bear
I believe this clue is a double definition.
'tolerate' is the first definition.
(synonyms)
'a beast' is the second definition.
(bear is a kind of beast)
(Other definitions for bear that I've seen before include "It could be polar or grizzly" , "Tolerate; animal" , "Paddington, Rupert" , "Put up with - speculator" , "live with" .)