Destroy documents rebels' leader kept in outhouse (5)
I believe the answer is:
shred
'destroy documents' is the definition.
(I've seen this in another clue)
'rebels' leader kept in outhouse' is the wordplay.
'leader' indicates taking the first letters.
'kept in' is an insertion indicator.
'outhouse' becomes 'shed' (I've seen this before).
The initial letter of 'rebels' is 'r'.
'r' placed within 'shed' is 'SHRED'.
(Other definitions for shred that I've seen before include "(Tear into) small piece(s)" , "Cut finely" , "Bit; cut or tear into tiny strips" , "Rip up" , "Tear; very small amount" .)