Delicacy could make one fretful (7)
I believe the answer is:
truffle
'delicacy' is the definition.
(I know that truffle is a type of candy)
'make one fretful' is the wordplay.
'make' indicates an anagram.
'fretful' is an anagram of 'TRUFFLE'.
'could' is the link.
(Other definitions for truffle that I've seen before include "Chocolaty sweet" , "2 (anag)" , "Edible fungus -- chocolate sweet" , "fungal growth" , "Rich food" .)