Have endless law enforcement groups (6)
I believe the answer is:
posses
'groups' is the definition.
'have endless' is the wordplay.
'have' becomes 'possess' (possessing is a kind of having).
'endless' means to remove the last letter.
'possess' with its final letter taken off is 'POSSES'.
'law enforcement' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for posses that I've seen before include "law enforcers" , "Sheriffs' men deputed to chase outlaws" , "forces for law and order" .)