Promiscuous people, wanting bit of privacy, slip away (5)
I believe the answer is:
elope
'slip away' is the definition.
(to elope is to run away to get married)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for elope that I've seen before include "Run away to wed" , "Do a runner" , "Run away to get married" , "leave with lover" , "Run away with one's beloved" .)