Substance in serenade, small amount (10)
I believe the answer is:
smattering
'small amount' is the definition.
(smattering can mean a small amount of something)
'substance in serenade' is the wordplay.
'substance' becomes 'matter' (synonyms).
'in' is an insertion indicator.
'serenade' becomes 'sing' (to serenade someone is to sing to them).
'matter' inserted inside 'sing' is 'SMATTERING'.
(Other definitions for smattering that I've seen before include "Hint" , "Little bit" , "Taste" , "little knowledge" , "Dash" .)