Goes along with on the second date (5)
I believe the answer is:
sides
'goes along' is the definition.
The answer and definition can be both to do with fundamental existence as well as being verbs in their -s form.
Perhaps there's an association between them I don't understand?
'on the second date' is the wordplay.
'on' says to put letters next to each other.
'the second' becomes 's' (common abbreviation).
'date' becomes 'ides' (I've seen this before).
's' put next to 'ides' is 'SIDES'.
'with' is the link.
Can you help me to learn more?
(Other definitions for sides that I've seen before include "Sports teams" , "Takes the part of someone in a dispute" , "Aspects" , "Lines" , "opponents?" .)