Demand on paper (7)
I believe the answer is:
require
'demand' is the definition.
(requiring is a kind of demanding)
'on paper' is the wordplay.
'on' becomes 're' ('on' can be mean 'with reference to').
'paper' becomes 'quire' (paper measurement**).
're'+'quire'='REQUIRE'
(Other definitions for require that I've seen before include "Need" , "Want, demand" , ".. must have" , "exact" , "26 [ORDER]" .)