Bunnies inside, hopping in boredom (5)
I believe the answer is:
ennui
'boredom' is the definition.
(synonyms)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for ennui that I've seen before include "Boredom, tedium" , "to make one list less when connected" , "depression" , "bore" , "Low interest rate" .)