Rewards, perhaps, on boarding public transport (7)
I believe the answer is:
bonuses
'rewards' is the definition.
(a bonus is a reward)
'on boarding public transport' is the wordplay.
'boarding' is an insertion indicator.
'public transport' becomes 'buses' (I've seen this before).
'on' going within 'buses' is 'BONUSES'.
'perhaps' is the link.
(Other definitions for bonuses that I've seen before include "Advantages" , "Extra payments for good work" , "benefits" .)