Warrant to “undeliver”? (7)

I believe the answer is:

deserve

'warrant' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

(Other definitions for deserve that I've seen before include "Show one is worthy" , "Warrant" , "Merit (something)" , "Merit, earn" , "Be entitled to" .)

I've seen this clue in The Times.

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