Send abroad from old harbour (6)
I believe the answer is:
export
'send abroad' is the definition.
'old harbour' is the wordplay.
'old' becomes 'ex'.
'harbour' becomes 'port' (I've seen this before).
'ex'+'port'='EXPORT'
'from' acts as a link.
(Other definitions for export that I've seen before include "Carry out of country" , "Send (goods) overseas" , "Send goods for sale abroad" , "Dispose of to another country" , "Sell or transfer abroad" .)