Sop that is Unite again (5)
I believe the answer is:
retie
'sop' is the definition.
The answer and definition can be both to do with contact as well as being verbs in their base form.
Maybe you can see a link between them that I don't see?
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for retie that I've seen before include "restore connection" , "Make knot or bow again" , "Link up again" , "make another knot" , "Bind again" .)