Plates holding British (English) loan certificates (10)
I believe the answer is:
debentures
'loan certificates' is the definition.
(financial term)
'plates holding british english' is the wordplay.
'plates' becomes 'dentures' (plates for holding false teeth).
'holding' indicates putting letters inside.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'english' becomes 'e' (abbreviation).
'b'+'e'='be'
'dentures' going around 'be' is 'DEBENTURES'.
(Other definitions for debentures that I've seen before include "Bonds" , "Shares" .)