Lie on setter’s newspaper (4)
I believe the answer is:
myth
'lie' is the definition.
(I've seen this before)
'on setter's newspaper' is the wordplay.
'on' is a charade indicator (letters next to each other).
'setter's' becomes 'my' (belonging to the crossword setter).
'newspaper' becomes 'th' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'my' put next to 'th' is 'MYTH'.
Can you help me to learn more?
(Other definitions for myth that I've seen before include "lie!" , "(Urban?) story" , "Fiction" , "Traditional allegory" , "Common false belief" .)