Exchanged for money in Ireland by Tristan's lover (6)
I believe the answer is:
Here is my best explanation:
'tristan's lover' is the definition.
(I've seen this before)
'exchanged for money in ireland' is the wordplay.
'exchanged for money' becomes 'sold' ('sell' can be a synonym of 'exchange for money').
'in' means one lot of letters goes inside another.
'ireland' becomes 'ie' (two letter country code).
'sold' put inside 'ie' is 'ISOLDE'.
'by' is the link.