Landlords delivered by postman? (7)
I believe the answer is:
letters
'landlords' is the definition.
(people who let property)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for letters that I've seen before include "Epistles" , "Written notes" , "landlords?" , "eg E G" , "Items of mail" .)