Merchant Seaman, say, pursuing quiet work (10)
I believe the answer is:
shopkeeper
'merchant' is the definition.
(I know that shopkeeper is a type of vendor)
'seaman say pursuing quiet work' is the wordplay.
'seaman say' becomes 'keeper' (I can't justify this - if you can you should believe this answer much more).
'pursuing' means one lot of letters go next to another.
'quiet' becomes 'sh' (both can be said to tell someone to be quiet).
'work' becomes 'op' (common abbreviation for 'opus').
'sh'+'op'='shop'
'keeper' put after 'shop' is 'SHOPKEEPER'.
Can you help me to learn more?
(Other definitions for shopkeeper that I've seen before include "Counter-agent" , "perhaps Napoleon's man in England?" , "E.g. newsagent" , "Tradesperson" .)