Let slip there isn't a feast (5)
I believe the answer is:
revel
'a feast' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for revel that I've seen before include "Take part in lively and noisy festivities" , "Take great pleasure" , "Riotous feast" , "Have noisy fun" , "Rejoice" .)