Tango with side-to-side movement? That's nonsense (7)
I believe the answer is:
twaddle
'that's nonsense' is the definition.
(informal term for nonsense or rubbish)
'tango with side-to-side movement?' is the wordplay.
'tango' becomes 'T' (phonetic alphabet: alpha, bravo, charlie etc.).
'with' is a charade indicator (letters next to each other).
'side-to-side movement?' becomes 'waddle' (type of walk).
't'+'waddle'='TWADDLE'
(Other definitions for twaddle that I've seen before include "Pretentious or silly talk" , "Claptrap" , "Piffle" , "Trivial speech or writing" , "bunk" .)