Musical sounds — new, in place of fine lady's bells (5)
I believe the answer is:
tones
'musical sounds' is the definition.
(musical tones)
'new in place of fine lady's bells' is the wordplay.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'in' is an insertion indicator.
'place of fine lady's bells' becomes 'toes' (nursery rhyme reference '...and bells on her toes').
'n' inserted within 'toes' is 'TONES'.
(Other definitions for tones that I've seen before include "Qualities of people's voices" , "Notes, characters" , "Qualities of colour, music or speech" , "Shades" , "Tints of colour" .)