Trail of paper at back of yard (4)
I believe the answer is:
drag
'trail' is the definition.
(I've seen this before)
'paper at back of yard' is the wordplay.
'paper' becomes 'rag' (rag is a kind of paper**).
'at' is a charade indicator (letters next to each other) (I've seen this in other clues).
'back of' says to take the final letters.
The last letter of 'yard' is 'd'.
'rag' after 'd' is 'DRAG'.
'of' is the link.
(Other definitions for drag that I've seen before include "Pull along forcefully" , "gay party" , "Tow" , "Resistance to motion" , "Bind" .)