Unusual race for paper (9)
I believe the answer is:
newsprint
'for paper' is the definition.
(newsprint is a kind of paper)
'unusual race' is the wordplay.
'unusual' becomes 'new' (new can mean unusual or different).
'race' becomes 'sprint' (I've seen this before).
'new'+'sprint'='NEWSPRINT'
(Other definitions for newsprint that I've seen before include "needed for the papers" , "Paper used by the Guardian or Daily Mirror, say" , "Print news on this kind of paper - what else?" , "Material for publication" , "Kind of paper this is produced on" .)