Rabbit to walk like a duck south of road junction (7)
I believe the answer is:
twaddle
'rabbit' is the definition.
(both can mean to talk foolishly)
'walk like a duck south of road junction' is the wordplay.
'walk like a duck' becomes 'waddle' (ducks waddle when they walk).
'south of' says to put letters next to each other.
'road junction' becomes 'T' (T-junction is a type of road junction).
'waddle' after 't' is 'TWADDLE'.
'to' acts as a link.
(Other definitions for twaddle that I've seen before include "Rubbish" , "Balderdash" , "Moonshine" , "Pretentious or silly talk" , "Drivel" .)