Individual going East (3)
I believe the answer is:
one
'individual' is the definition.
'going east' is the wordplay.
'going' becomes 'on' (both can mean functioning or activated).
'east' becomes 'e' ('E' can be a synonym of 'east').
'on'+'e'='ONE'
(Other definitions for one that I've seen before include "Ace" , "A certain; single person" , "Half of two" , "SECOND PART OF 16" , "1" .)