Accepts Yankee on board public transport (4)
I believe the answer is:
buys
'accepts' is the definition.
(buying is a kind of accepting)
'yankee on board public transport' is the wordplay.
'yankee' becomes 'Y' (phonetic alphabet: alpha, bravo, charlie etc.).
'on board' means one lot of letters goes inside another (inserted letters are taken on board).
'public transport' becomes 'bus' (bus is a kind of public transport).
'y' inserted inside 'bus' is 'BUYS'.
(Other definitions for buys that I've seen before include "pays the price" , "Spends money" , "Purchases" .)