Snooty Isabella did appear in part (2-2-2)
I believe the answer is:
'snooty' is the definition.
(I know that snooty can be written as la-di-da)
'isabella did appear in part' is the wordplay.
'in part' indicates a hidden word.
'LA-DI-DA' is hidden within 'isabella did appear'.
(Other definitions for la-di-da that I've seen before include "Stuck-up" , "I'd a lad with affected manner or pronunciation" , "Informally, having affected manner of pronunciation" , "Pretentious, snobbish" , "Hoity-toity" .)