Answered the salesman with a song (7)
I believe the answer is:
replied
'answered' is the definition.
('reply' can be a synonym of 'answer')
'salesman with a song' is the wordplay.
'salesman' becomes 'rep' (sales representative).
'with' means one lot of letters go next to another.
'a song' becomes 'lied' (type of German song).
'rep'+'lied'='REPLIED'
'the' acts as a link.
(Other definitions for replied that I've seen before include "Answered back" , "Wrote back" , "Made some response" , "Responded" , "Gave answer" .)