Runner hiding in Enniskillen (3)
I believe the answer is:
ski
'runner' is the definition.
(something which 'runs', ie moves quickly on snow)
'hiding in enniskillen' is the wordplay.
'hiding in' says to take the centre.
The middle letters of 'enniskillen' are 'SKI'.
(Other definitions for ski that I've seen before include "Narrow runner for snow and water" , "Journey" , "the end for many Russians" , "Winter sport equipment" , "Winter-sports item" .)