Bank role propping up pound (7)
I believe the answer is:
rampart
'bank' is the definition.
(thesaurus)
'role propping up pound' is the wordplay.
'role' becomes 'part' (eg a part or role in a film).
'propping up' means one lot of letters go next to another (in a down clue, some letters hold others up).
'pound' becomes 'ram' (synonyms).
'part' after 'ram' is 'RAMPART'.
(Other definitions for rampart that I've seen before include "Pain-relieving drug" , "Battlement, fortification" , "Military protection" , "Defensive earthwork" , "Broad defensive wall" .)