Bank with millions? Pound, not pence (5)
I believe the answer is:
mound
'bank' is the definition.
(a bank of earth)
'millions? pound not pence' is the wordplay.
'millions?' becomes 'm' (abbreviation).
'not' suggests deleting specific letters.
'pence' becomes 'p'.
'pound' with 'p' taken away is 'ound'.
'm'+'ound'='MOUND'
'with' acts as a link.
(Other definitions for mound that I've seen before include "Knoll" , "Earth bank" , "Small hill, large pile" , "Mass of piled-up earth or stones" , "Hillock; gold ball (Her.)" .)