Man is a hill-dweller, working (5)
I believe the answer is:
anton
'man' is the definition.
(I've seen this before)
'hill-dweller working' is the wordplay.
'hill dweller' becomes 'an't' (I've seen this in another clue).
'working' becomes 'on' (on can mean working or activated).
'ant'+'on'='ANTON'
'is a' is the link.
(Other definitions for anton that I've seen before include "-- Chekhov, Russian dramatist" , "- Chekhov, playwright" , "man" , "Rodgers perhaps" , "..... Chekov" .)