Doorbell broken -- here one's invited to knock! (8)
I believe the answer is:
bordello
'here one's invited to knock?' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
'doorbell broken' is the wordplay.
'broken' is an anagram indicator.
'doorbell' is an anagram of 'BORDELLO'.
Can you help me to learn more?
(Other definitions for bordello that I've seen before include "House of ill repute" , "Disorderly house" , "Knocking shop" , "Brothel" , "Where one pays for the other" .)