Separate from last partner after Steve goes shirtless (5)

I believe the answer is:

sever

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'separate' is the definition.
(sever can mean to split or separate)

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

(Other definitions for sever that I've seen before include "Cut right off" , "Verse (anag)" , "Cleave" , "Divide by cutting" , "Cut into parts" .)

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

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