… royals of note overwhelmed by costs (7)
I believe the answer is:
princes
'royals' is the definition.
(prince is a kind of royal)
'note overwhelmed by costs' is the wordplay.
'note' becomes 'n' (abbreviation).
'overwhelmed by' indicates putting letters inside (I've seen this in other clues).
'costs' becomes 'prices' ('price' can be a synonym of 'cost').
'n' going inside 'prices' is 'PRINCES'.
'of' acts as a link.
(Other definitions for princes that I've seen before include "Male royals" , "king's followers?" .)