Chattering (9)

I think it could be either:

gibbering

prattling

'chattering' is the definition.
('gibber' can be a synonym of 'chatter')

This is all the clue.

(Other definitions for gibbering that I've seen before include "Raving" , "Prattling" , "Blathering" .)

I've seen this clue in the Sydney Morning Herald and the Evening Standard.

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