Join you the night after, say (5)
I believe the answer is:
'join' is the definition.
(I know that join can be written as unite)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for unite that I've seen before include "Pull together" , "Gather together as one" , "Amalgamate" , "Link" , "Bring together, become one" .)