Admit leaving College Green (5)
I believe the answer is:
allow
'admit' is the definition.
(allowing is a kind of admiting)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for allow that I've seen before include "Permit or concede" , "Permit or agree" , "Tolerate" , "Grant" , "Sanction" .)