On paper it makes things look very black (6,3)
I believe the answer is:
indian ink
'it makes things look very black' is the definition.
The definition suggests a singular noun which matches the answer.
'on paper' is the wordplay.
I cannot really understand how this works, but
'paper' could be 'india' (india paper is a kind of paper) and 'india' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for indian ink that I've seen before include "Maybe part of squid" , "Writing fluid containing carbon particles" , "Draw with this" , "Deep black writing fluid" , "black pigment" .)