Coastal road (some might say) is capital (6)
I believe the answer is:
beirut
'capital' is the definition.
(Beirut is an example)
'coastal road some might say is' is the wordplay.
I cannot quite understand how this works, but
'road' could be 'rut' (rut is a kind of road) and 'rut' is found within the answer.
'is' could be 'be' and 'be' is found in the answer.
A single letter 'i' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for beirut that I've seen before include "Middle East capital" , "Lebanon's capital" , "Capital city of Lebanon" , "Lebanese capital" , "Capital of 21 across" .)