Mouthful of sugar, initially, and syrup (4)
I believe the answer is:
swig
'mouthful' is the definition.
The answer and definition can be both things that one consumes for nourishment as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'sugar initially and syrup' is the wordplay.
'initially' says to take the initial letters.
'and' says to put letters next to each other.
'syrup' becomes 'wig' ('syrup of fig' is Cockney rhyming slang for 'wig').
The initial letter of 'sugar' is 's'.
's'+'wig'='SWIG'
'of' is the link.
Can you help me to learn more?
(Other definitions for swig that I've seen before include "Large draught of drink" , "Swallow drink hurriedly" , "Drink (a deep draught)" , "Drink deeply" , "Drink in large draughts" .)