A paper handkerchief is being discussed (2,5)
I believe the answer is:
at issue
'being discussed' is the definition.
(I've seen this before)
'a paper handkerchief' is the wordplay.
'paper handkerchief' becomes 'tissue' (I've seen this before).
'a'+'tissue'='AT ISSUE'
'is' is the link.
(Other definitions for at issue that I've seen before include "Being discussed or disputed" , "Questionable" , "in dispute" , "In question, under discussion" , "under debate" .)