Sell abroad last of merchandise: ten left (6)
I believe the answer is:
export
'sell abroad' is the definition.
('export' can be a synonym of 'sell abroad')
'last of merchandise ten left' is the wordplay.
'last of' indicates one should take the final letters.
'ten' becomes 'x' (roman numeral).
'left' becomes 'port' (left side of a ship - opposite of starboard).
The last letter of 'merchandise' is 'e'.
'e'+'x'+'port'='EXPORT'
(Other definitions for export that I've seen before include "Dispose of to another country" , "Carry out of country" , "Send goods for sale abroad" , "Sell or give to another country" , "strong brown beer" .)