Bank worker gets sack (7)
I believe the answer is:
cashier
I believe this clue is a double definition.
'bank worker' is the first definition.
(I've seen this before)
'sack' is the second definition.
(I've seen this before)
'gets' is the link.
(Other definitions for cashier that I've seen before include "money dispenser" , "one taking money" , "Teller - dismiss in disgrace" , "Discharge" , "Employee who takes in or gives out money" .)