Let slip there isn't a feast (5)
I believe the answer is:
revel
'feast' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
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" .)