Set to falsify papers (5)
I believe the answer is:
rigid
'set' is the definition.
(I know that set can be written as rigid)
'falsify papers' is the wordplay.
'falsify' becomes 'rig'.
'papers' becomes 'ID' (identification papers).
'rig'+'id'='RIGID'
'to' acts as a link.
(Other definitions for rigid that I've seen before include "starched too much?" , "stern" , "Stiff, unmoving" , "Frozen" , "Firmly fixed" .)