In appearance, possibly, it may be torn (5)
I believe the answer is:
paper
'in' is the definition.
The answer and definition can be both substances as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for paper that I've seen before include "conference presentation" , "Dissertation" , "Scholarly article" , "News medium" , "Set of written exam questions" .)