He struggles with valiant monstrous beast (9)

I believe the answer is:

leviathan

'monstrous beast' is the definition.
(I've seen this before)

'he struggles with valiant' is the wordplay.
'struggles with' is an anagram indicator.
'he' with its letters mixed up with 'valiant' gives 'LEVIATHAN'.

(Other definitions for leviathan that I've seen before include "Biblical sea monster" , "Gigantic" , "Autocratic monarch" , "Monstrous sea creature" , "Monstrous beast" .)

I've seen this clue in The Globe and Mail.

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