Old money at court vanished (7)
I believe the answer is:
extinct
'vanished' is the definition.
(thesaurus)
'old money at court' is the wordplay.
'old' becomes 'ex'.
'money' becomes 'tin' (I've seen this before**).
'at' means one lot of letters go next to another.
'court' becomes 'ct'.
'ex'+'tin'+'ct'='EXTINCT'
(Other definitions for extinct that I've seen before include "killed off completely" , "Dead (as a dodo?)" , "Of volcano, no longer active" , "never to be seen again" , "Defunct" .)