Former partner left ship (6)
I believe the answer is:
export
'ship' is the definition.
(thesaurus)
'former partner left' is the wordplay.
'former partner' becomes 'ex' (an ex-partner).
'left' becomes 'port' (left side of a ship - opposite of starboard).
'ex'+'port'='EXPORT'
(Other definitions for export that I've seen before include "Sell or transfer abroad" , "ship overseas" , "Send goods for sale abroad" , "Send (goods) overseas" , "Dispose of to another country" .)