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 before)
'up for tea not yellow' is the wordplay.
'up' is an anagram indicator.
'not' indicates named letters should be taken away.
'yellow' becomes 'or' (heraldic term).
'fortea' with 'or' taken out is 'ftea'.
'ftea' anagrammed gives 'FETA'.
'served' is the link.
(Other definitions for feta that I've seen before include "White Greek cheese", "10 down cheese", "Cheese", "Salty Greek cheese", "Goat's or sheep's milk cheese", "Greek cheese from goat or sheep milk", "White and salty goat or sheep cheese", "Crumbly Greek cheese", "Greek salad cheese" and "Eastern Mediterranean cheese".)