Royal Engineer's forged papers (6)
I believe the answer is:
sapper
'royal engineer's' is the definition.
(I've seen this before)
'forged papers' is the wordplay.
'forged' indicates anagramming the letters.
'papers' anagrammed gives 'SAPPER'.
(Other definitions for sapper that I've seen before include "Royal Engineer" , "Writer" , "Soldier who digs trenches" , "Military engineer" , "Private soldier in the Royal Engineers" .)