Half-hearted cry of derision when meeting snake and rodent (6)

I believe the answer is:

jerboa

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'rodent' is the definition.
(jerboa is a kind of rodent)

I don't understand the remainder of the clue.

(Other definitions for jerboa that I've seen before include "Desert rodent" , "Mouse-like jumping rodent - ear job (anag)" , "Desert-dwelling rodent" .)

I've seen this clue in The Times.

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