A disposable hanky under discussion (2,5)

I believe the answer is:

at issue

'under discussion' is the definition.
(I've seen this before)

'a disposable hanky' is the wordplay.
'disposable hanky' becomes 'tissue'.
'a'+'tissue'='AT ISSUE'

(Other definitions for at issue that I've seen before include "In question, under discussion" , "under debate" , "Questionable" , "in dispute" , "Being discussed or disputed" .)

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