Don't lose can (8)

I believe the answer is:

preserve

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'can' is the definition.
(preserve in a can)

I cannot understand how the remainder of the clue works.

(Other definitions for preserve that I've seen before include "Guard" , "kipper?" , "area where game is held" , "Toast option" , "Keep alive; jam" .)

I've seen this clue in The Sun.

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