On tramp, force paperwork (4)
I believe the answer is:
bumf
'paperwork' is the definition.
(bumf means printed material)
'on tramp force' is the wordplay.
'on' says to put letters next to each other.
'tramp' becomes 'bum' (both can mean a homeless person).
'force' becomes 'F' (symbol used in Physics e.g. f=ma).
'bum'+'f' is 'BUMF'.
(Other definitions for bumf that I've seen before include "Junk-mail" , "Too much information!" , "Useless printed documents" , "Printed material" , "official papers?" .)