Calms down a beast, somehow (6)
I believe the answer is:
abates
'calms down' is the definition.
(I've seen this in another clue)
'a beast somehow' is the wordplay.
'somehow' indicates anagramming the letters.
'beast' anagrammed gives 'bates'.
'a'+'bates'='ABATES'
(Other definitions for abates that I've seen before include "Becomes less severe or strong" , "moderates" , "Slacks off" , "Becomes less strong like storm" , "Goes down like storm" .)