Feast on an egg! (6)
I believe the answer is:
easter
'feast' is the definition.
(I've seen this before)
'an egg' is the wordplay.
I cannot quite see how this works, but
'an' could be 'a' and 'a' is located in the answer.
The remaining letters 'ester' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'on' is the link.
Can you help me to learn more?
(Other definitions for easter that I've seen before include "Sort of tide" , "A terse sort of Spring festival?" , "Christian celebration of the Resurrection" , "Snug retreat" , "Card, egg or Island" .)