Suit what athletes train to do (5)

I believe the answer is:

befit

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'suit' is the definition.
(I know that suit can be written as befit)

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

(Other definitions for befit that I've seen before include "Become, suit" , "Be appropriate for" , "Be right and suitable for" .)

I've seen this clue in the Evening Standard.

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