How a runner can blossom (6)

I believe the answer is:

flower

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'blossom' is the definition.
('flower' can be a synonym of 'blossom')

I don't understand the remainder of the clue.

(Other definitions for flower that I've seen before include "Garden plant" , "One found in bed perhaps" , "Bloom" , "prime of life" , "the best one can pick" .)

I've seen this clue in the Evening Standard.

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