To cut or reduce severely (5)

I believe the answer is:

sever

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'to cut' is the definition.
(severing is a kind of cutting)

I don't understand how the rest of the clue works.

(Other definitions for sever that I've seen before include "Cut off suddenly" , "Divorce" , "Divide, cut" , "Cut completely" , "Put an end to (connection or relationship)" .)

I've seen this clue in the Evening Standard.

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