Mails bills without hesitation (5)
I believe the answer is:
posts
'mails' is the definition.
('post' can be a synonym of 'mail')
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for posts that I've seen before include "Jobs and poles" , "Is dispatching" , "Stakes" , "Sends by mail" , "Mails the uprights?" .)