Payment at the door leading to a passage (4)
I believe the answer is:
coda
'passage' is the definition.
(I've seen this before)
'payment at the door leading to a' is the wordplay.
'payment at' becomes 'co' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'leading' says to take the initial letters.
The initial letter of 'door' is 'd'.
'co'+'d'+'a'='CODA'
Can you help me to learn more?
(Other definitions for coda that I've seen before include "Musical recap" , "final piece of work" , "Final movement" , "Closing passage of a piece of music" , "Closing stage" .)