Harry's at play running around for paper (9)
I believe the answer is:
anaglypta
'paper' is the definition.
Both the answer and definition are singular nouns.
Perhaps you can see a link between them that I don't see?
'harry's at play running around' is the wordplay.
'harry' becomes 'nag' ('harry' can mean 'to persistently bother').
'running' indicates anagramming the letters.
'around' is an insertion indicator.
'at'+'play'='atplay'
'atplay' with letters rearranged gives 'alypta'.
'nag' put within 'alypta' is 'ANAGLYPTA'.
'for' is the link.
Can you help me to learn more?
(Other definitions for anaglypta that I've seen before include "paper with bosses" , "Thick embossed wallpaper" .)