Time together to become less intense, they say (4)
I believe the answer is:
sync
'time together' is the definition.
(to sync is to time something in synchrony)
'become less intense they say' is the wordplay.
'become less intense' becomes 'sink' (sink can mean to drop or decrease in strength).
'they say' shows a homophone (sound like).
'sink' sounds like 'SYNC'.
'to' is the link.
(Other definitions for sync that I've seen before include "Togetherness (of sound and picture, say)" , "Unison (abbrev.)" , "Agreement in time" , "In which one's matching" , "In which things occur simultaneously" .)