Time to walk like a duck? Nonsense! (7)
I believe the answer is:
twaddle
'nonsense' is the definition.
(informal term for nonsense or rubbish)
'time to walk like a duck?' is the wordplay.
'time' becomes 't' (abbreviation).
'to walk like a duck?' becomes 'waddle' (ducks waddle when they walk).
't'+'waddle'='TWADDLE'
(Other definitions for twaddle that I've seen before include "Foolish talk" , "Foolish words" , "Drivel" , "Pretentious or silly talk" , "tripe" .)