Howl about unaccompanied twaddle (7)
I believe the answer is:
baloney
'twaddle' is the definition.
(synonyms)
'howl about unaccompanied' is the wordplay.
'howl' becomes 'bay' (I've seen this before).
'about' indicates putting letters inside.
'unaccompanied' becomes 'lone' (on one's own).
'bay' enclosing 'lone' is 'BALONEY'.
(Other definitions for baloney that I've seen before include "deceptive talk" , "Nonsense; lean yob (anag)" , "foolish talk!" , "rhubarb" , "Tosh" .)