Staff regret accepting European money (7)
I believe the answer is:
retinue
'staff' is the definition.
(thesaurus)
'regret accepting european money' is the wordplay.
'regret' becomes 'rue' ('rue' can be a synonym of 'regret').
'accepting' means one lot of letters goes inside another.
'european' becomes 'e' (abbreviation e.g. EU).
'money' becomes 'tin' (I've seen this before**).
'e'+'tin'='etin'
'rue' placed around 'etin' is 'RETINUE'.
(Other definitions for retinue that I've seen before include "Train, following" , "Body of aides" , "Attendants, followers" , "Entourage, followers" , "Group of followers" .)