Deaden feeling in bottom, cycling around on tail of criminal, mostly (6)

I believe the answer is:

benumb

'deaden feeling' is the definition.

I cannot understand how the remainder of the clue works.

(Other definitions for benumb that I've seen before include "Make dazed or unfeeling" , "Stun" , "Deprive of feeling" , "Maybe anaesthetise" .)

I've seen this clue in The Guardian.

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