Words of affection mean zilch in confectionery (5,8)
I believe the answer is:
sweet nothings
'words of affection' is the definition.
(I've seen this before)
'zilch in confectionery' is the wordplay.
'zilch' becomes 'nothing' (synonyms).
'in' is an insertion indicator.
'confectionery' becomes 'sweets' (I've seen this before).
'nothing' placed inside 'sweets' is 'SWEET NOTHINGS'.
'mean' acts as a link.
(Other definitions for sweet nothings that I've seen before include "Lovers' words?" , "Amorous burble" , "I would love to say these" , "stuff for Valentine cards" , "Whispered endearments" .)