Cancel rapper insisting on gun clemency in seconds (5)

I believe the answer is:

annul

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'cancel' is the definition.
(I know that annul is a type of cancel)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for annul that I've seen before include "Cancel, abolish" , "Countermand" , "Cancel, say a law" , "Cancel, revoke" , "Obligation" .)

I've seen this clue in the Sydney Morning Herald.

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