Group helping the sheriff (5)
I believe the answer is:
posse
'group helping the sheriff' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for posse that I've seen before include "Group aiding lawman" , "Law-enforcers" , "Band supporting sheriff" , "Group formed by sheriff" , "Band of people involved in some activity" .)