Was her betrothal somewhat sweet? (7)
I believe the answer is:
sherbet
'sweet?' is the definition.
(sherbet is a kind of sweet)
'was her betrothal somewhat' is the wordplay.
'somewhat' indicates the answer is hidden within the clue.
'SHERBET' can be found hidden inside 'was her betrothal'.
(Other definitions for sherbet that I've seen before include "Sweet fizzy powder" , "Sweet effervescent powder" , "iced food" , "Sweet fizzy, fruity, drink" , "Powder for making fizzy drink" .)