Ancient city infiltrating large state again works on paper (10)
I believe the answer is:
literature
'works on paper' is the definition.
'literature' can be an answer for 'paper' (thesaurus). I am unsure of the 'works on' bit.
'ancient city infiltrating large state again' is the wordplay.
'ancient city' becomes 'ur' (ancient Sumerian city state).
'infiltrating' means one lot of letters goes inside another.
'large' becomes 'L' (eg in clothes sizes).
'state again' becomes 'iterate' (I've seen this in another clue).
'l'+'iterate'='literate'
'ur' put into 'literate' is 'LITERATURE'.
Can you help me to learn more?
(Other definitions for literature that I've seen before include "Creative writing" , "Printed matter" , "writer's work" , "Written material" , "Work by Spenser for instance" .)