Post for men, by the sound of it (4)
I believe the answer is:
'post' is the definition.
(I know that post can be written as mail)
'for men by the sound of it' is the wordplay.
'for men' becomes 'male'.
'by the sound of it' shows a homophone (sound like).
'male' sounds like 'MAIL'.
(Other definitions for mail that I've seen before include "Post in America" , "Letters and parcels" , "some self-defence material" , "Letters - armour" , "Chain armour" .)