Criticise American lawyer for being a beast (5)
I believe the answer is:
panda
'a beast' is the definition.
(I've seen this before)
'criticise american lawyer' is the wordplay.
'criticise' becomes 'pan' (informal term meaning to criticise heavily).
'american lawyer' becomes 'DA' (abbreviation for 'District Attorney').
'pan'+'da'='PANDA'
'for being' is the link.
(Other definitions for panda that I've seen before include "One reluctant to mate" , "Black and white animal" , "Black and white mammal" , "Chinese animal" , "Chinese native" .)