Revealing postal orders kept by former Dutch bank (8)
I believe the answer is:
exposing
'revealing' is the definition.
(exposing is a kind of revealing)
'postal orders kept by former dutch bank' is the wordplay.
'postal orders' becomes 'pos' (PO is an abbreviation for 'postal order').
'kept by' means one lot of letters goes inside another.
'former' becomes 'ex'.
'dutch bank' becomes 'ing' (ING Group, Dutch banking corporation).
'ex'+'ing'='exing'
'pos' inserted into 'exing' is 'EXPOSING'.
(Other definitions for exposing that I've seen before include "Uncovering" , "Showing up" , "outing" , "Subjecting to light, making known" .)