Lover eats bit of lemon tart (4)
I believe the answer is:
flan
'tart' is the definition.
(type of tart)
'lover eats bit of lemon' is the wordplay.
'lover' becomes 'fan' (synonyms).
'eats' means one lot of letters goes inside another.
'bit of' indicates taking the first letters.
The initial letter of 'lemon' is 'l'.
'fan' going around 'l' is 'FLAN'.
(Other definitions for flan that I've seen before include "Baked and filled pastry case dish" , "Baked dish filled with fruit or custard" , "Quiche-like dish" , "it may get jammed" , "Open-topped pastry dish" .)