Under debate
'under debate' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for at issue that I've seen before include "Being discussed or disputed" , "in dispute" , "under debate" , "In question, under discussion" , "Questionable" .)
'under debate' is the definition.
(I've seen this in another clue)
This is all the clue.