Not used to run on paper (9)
I believe the answer is:
newsprint
'paper' is the definition.
(newsprint is a kind of paper)
'not used to run on' is the wordplay.
'not used' becomes 'new' (I've seen this in another clue).
'to run' becomes 'sprint' (sprinting is a kind of running).
'on' says to put letters next to each other.
'new'+'sprint'='NEWSPRINT'
(Other definitions for newsprint that I've seen before include "cheap paper" , "needed for the papers" , "Material for publication" , "Print news on this kind of paper - what else?" , "sports pages and much else" .)