Stick together -- or split (6)
I believe the answer is:
cleave
This clue is a double definition.
'stick together' is the first definition.
(thesaurus)
'split' is the second definition.
(I know that split can be written as cleave)
'or' acts as a link.
(Other definitions for cleave that I've seen before include "Split or cling to" , "Stick fast; split" , "remain attached" , "To separate and to adhere" , "Adhere or split apart" .)