They're mine workers on leave (5,3)
I believe the answer is:
hands off
'they're mine' is the definition.
(both express possessiveness)
'workers on leave' is the wordplay.
'workers' becomes 'hands' (hand is a kind of worker).
'on leave' becomes 'off' (off work).
'hands'+'off'='HANDS-OFF'
(Other definitions for hands off that I've seen before include "Operated by remote control" , "Don't touch!" , "Not getting involved" , "Don't interfere" .)