Swap over shillings or sixpences, say (8)
I believe the answer is:
exchange
This might be a double definition.
'swap over' is the first definition.
'exchange' can be an answer for 'swap' (I've seen this before). I am not sure about the 'over' bit.
'shillings or sixpences say' is the second definition.
(old money or ex-change)
(Other definitions for exchange that I've seen before include "Altercation" , "Swap, barter" , "truck" , "Price of one currency in another" , "Convert" .)