Source of paper cups: it's a recycled paper (8)
I believe the answer is:
treatise
'paper' is the definition.
(thesaurus)
'source of paper' is the wordplay.
'source' becomes 'treat' (I have seen 'Source of gratification' mean 'treat' so perhaps 'source' could also mean 'treat').
'of paper' becomes 'ise' (I can't justify this - if you can you should give a lot more credence to this answer).
'treat'+'ise'='TREATISE'
'cups it's a recycled' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for treatise that I've seen before include "Formal exposition" , "Formal written work dealing with a particular subject" , "Written study" , "Written composition" , "Formal piece of writing on a particular subject" .)