It's served in a white apron (3)
I believe the answer is:
tea
'it's' is the definition.
I can't judge whether this defines the answer.
'in a white apron' is the wordplay.
'in' says the answer is hidden in the clue.
'TEA' is hidden in the letters of 'white apron'.
'served' acts as a link.
Can you help me to learn more?
(Other definitions for tea that I've seen before include "Afternoon meal; drink" , "Light afternoon meal" , "A light meal - eat up" , "Plant" , "Plantation product" .)