Cheese served up for tea — not yellow (4)
I believe the answer is:
Here is my best explanation:
'cheese' is the definition.
(I've seen this in other clues)
'up for tea not yellow' is the subsidiary indication.
'up' indicates anagramming the letters.
'not' suggests deleting specific letters.
'yellow' becomes 'or' (heraldic term).
'fortea' with 'or' taken away is 'ftea'.
'ftea' with letters rearranged gives 'feta'.
'served' is the link.
(Other definitions for feta that I've seen before include "White Greek cheese", "10 down cheese", "food there", "Salty Greek cheese", "Greek sheep or goats' cheese", "Greek cheese from goat or sheep milk", "Goat's or sheep's milk cheese", "A Greek cheese", "Greek dairy product" and "Crumbly Greek cheese".)