Yours truly, large and offensive? Sweet! (9)
I believe the answer is:
melodious
'sweet' is the definition.
(similar in meaning)
'yours truly large and offensive?' is the wordplay.
'yours truly' becomes 'me' (the person who set this crossword).
'large' becomes 'L' (eg in clothes sizes).
'and' is a charade indicator (letters next to each other).
'offensive?' becomes 'odious' (I've seen this before).
'me'+'l'+'odious'='MELODIOUS'
(Other definitions for melodious that I've seen before include "Sweet'" , "music to the ears!" , "Tuneful" .)