Followers regret holding on to European money (7)
I believe the answer is:
retinue
'followers' is the definition.
(thesaurus)
'regret holding on to european money' is the wordplay.
'regret' becomes 'rue' ('rue' can be a synonym of 'regret').
'holding' indicates putting letters inside.
'on' means one lot of letters go next to another.
'to european' becomes 'e' (abbreviation e.g. EU).
'money' becomes 'tin' (I've seen this before**).
'e' put next to 'tin' is 'etin'.
'rue' going around 'etin' is 'RETINUE'.
(Other definitions for retinue that I've seen before include "Group of followers" , "Figure out" , "Cortege" , "Train, following" , "Attendants, followers" .)