A follower employs public transport (5)
I believe the answer is:
buses
'public transport' is the definition.
(I've seen this before)
'a follower employs' is the wordplay.
'a follower' becomes 'b' ('b' is the follower of 'a' in the alphabet**).
'employs' becomes 'uses' ('use' can be a synonym of 'employ').
'b'+'uses'='BUSES'
(Other definitions for buses that I've seen before include "Public service vehicles" , "Public transport vehicles" , "Passenger vehicles" .)