Contractor perhaps also on leave (7)
I believe the answer is:
abandon
'leave' is the definition.
(to abandon is to leave or desert)
'contractor perhaps also on' is the wordplay.
'contractor perhaps' becomes 'aband' (I can't justify this - if you can you should give a lot more credence to this answer).
'also' is a charade indicator (letters next to each other).
'aband'+'on'='ABANDON'
Can you help me to learn more?
(Other definitions for abandon that I've seen before include "Desert; give up (action)" , "Wantonness: desert" , "Czech city" , "Desert; intemperance" , "Desert or yield without restraint" .)