Confectioner with HM warrants for spongy sweets (12)
I believe the answer is:
marshmallows
'for spongy sweets' is the definition.
(I've seen this before)
'confectioner with hm' is the wordplay.
I cannot quite see how this works, but
'with' could be 'w' (abbreviation) and 'w' is found within the answer.
'hm' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'warrants' acts as a link.
Can you help me to learn more?
(Another definition for marshmallows that I've seen is " Spongy, gelatin-filled sweets".)