The coach takes us to Birkenhead (3)
I believe the answer is:
bus
'the coach' is the definition.
('bus' can be a synonym of 'coach')
'us to birkenhead' is the wordplay.
'to' says to put letters next to each other (I've seen this in other clues).
'birkenhead' becomes 'b' (head letter of 'birken').
'us' after 'b' is 'BUS'.
'takes' is the link.
(Other definitions for bus that I've seen before include "Means of public transport" , "People carrier" , "Road vehicle able to carry many passengers" , "Charabanc" , "Motor-coach" .)