Can opening motif become so sweet? (6)
I believe the answer is:
comfit
'sweet?' is the definition.
(comfit is a kind of sweet)
'can opening motif become' is the wordplay.
'opening' suggests taking the first letters.
'become' indicates an anagram.
The first letter of 'can' is 'c'.
'motif' with letters rearranged gives 'omfit'.
'c'+'omfit'='COMFIT'
'so' is the link.
(Other definitions for comfit that I've seen before include "Candied fruit" , "Sweet consisting of nut in sugar" , "Kind of sweet, nut in sugar" , "Sweet - MFI cot (anag)" .)