Added condition for one on a bicycle (5)

I believe the answer is:

rider

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'added condition' is the definition.
(I've seen this before)

I can't explain the remainder of the clue.

(Other definitions for rider that I've seen before include "Legal document's additional clause" , "Horseman or cyclist" , "Motorcyclist" , "Jockey" , "Jury's added comment" .)

I've seen this clue in The Guardian.

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