He's big in Westminster, very big in Scotland (3)
I believe the answer is:
'he's' is the definition.
(I've seen this in another clue)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for ben that I've seen before include "Scottish mountain peak" , "High mountain (Scots)" , "Mountain; man's name" , "Big . . . is a famous London clock-tower" , "Second part of 11" .)