Protected documents a felon guards (4)
I believe the answer is:
safe
'protected' is the definition.
(similar in meaning)
'documents a felon guards' is the wordplay.
'guards' indicates the answer is hidden within the clue.
'SAFE' can be found hidden inside 'documents a felon'.
(Other definitions for safe that I've seen before include "Metal box for storing valuables in" , "Strongbox; secure" , "Secure - place to keep valuables" , "Unharmed" , "Secure in metal box?" .)