Concept used in wide arena (4)
I believe the answer is:
idea
'concept' is the definition.
(I've seen this before)
'in wide arena' is the wordplay.
'in' indicates the answer is hidden within the clue.
'IDEA' can be found hidden inside 'wide arena'.
'used' is the link.
(Other definitions for idea that I've seen before include "Sudden inspiration?" , "Notion, concept" , "It comes to mind" , "Intention" , "Plato's Form is" .)