Climbers: there are five in the Olympic Village but only one in an event (9)
I believe the answer is:
ascenders
'climbers' is the definition.
(people making an ascent)
'there are five in the olympic village but only one in an event' is the wordplay.
I cannot quite understand how this works, but
'are' could be 'a' (short for 'are', historical unit of measurement) and 'a' is found in the answer.
'event' could be 'end' (end is a kind of event) and 'end' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for ascenders that I've seen before include "odd bits of Tibet, for example" , "We climb" .)