Clearly establishes claws and feathers (5,4)

I believe the answer is:

nails down

'clearly establishes' is the definition.
(to nail something down is to establish it clearly)

'claws and feathers' is the wordplay.
'claws' becomes 'nails' (I've seen this before).
'and' means one lot of letters go next to another.
'feathers' becomes 'down' (down can mean bird feathers).
'nails'+'down'='NAILS DOWN'

(Another definition for nails down that I've seen is " Clearly defines".)

I've seen this clue in The Telegraph.

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