Crossword Genius

Foreign currency earners in old harbour towns? (7)

Ross

I believe the answer is:

exports

I'm a little stuck... Click here to teach me more about this clue!

'foreign currency earners' is the definition.
(I've seen this before)

'old harbour towns?' is the wordplay.
'old' becomes 'ex'.
'harbour towns?' becomes 'ports' (I can't justify this - if you can you should believe this answer much more).
'ex'+'ports'='EXPORTS'

'in' acts as a link.

Can you help me to learn more?

(Other definitions for exports that I've seen before include "Goods or services sold abroad" , "goods going abroad" , "Foreign currency earners" , "Imports & - -" , "sends abroad" .)

I've seen this clue in The Telegraph.
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