Lock horns and snarl (6)
I believe the answer is:
tangle
This clue is a double definition.
'lock horns' is the first definition.
(I've seen this in another clue)
'snarl' is the second definition.
(I know that snarl can be written as tangle)
'and' is the link.
(Other definitions for tangle that I've seen before include "Confused mess" , "'Twisted mess, muddle (6)'" , "At glen (anag.)" , "Complicated mess" , "Snarl or embroil" .)