Stick or hold together (6)
I believe the answer is:
cohere
I believe this clue is a double definition.
'stick' is the first definition.
(I know that stick can be written as cohere)
'hold together' is the second definition.
(I've seen this in another clue)
(Other definitions for cohere that I've seen before include "Hold firmly together" , "Be consistent" , "Hang together" , "Stick together, remain united" , "Fit together" .)