Burns maybe lacking energy and time to blether on (6)

I believe the answer is:

rabbit

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'blether on' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for rabbit that I've seen before include "family pet?" , "Fast-breeding hopper" , "Weak player" , "Furry, burrowing animal" , "Meat" .)

I've seen this clue in The Independent.

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