In conversation, much time shared by you and me (4)
I believe the answer is:
ours
'shared by you and me' is the definition.
(I've seen this in another clue)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for ours that I've seen before include "Relating or belonging to us" , "What we share" , "The French bear" , "Indiscriminate slaughter" , "Belong to us both" .)