Stronghold in Banff or Toronto (4)
I believe the answer is:
fort
'stronghold' is the definition.
(I've seen this in another clue)
'in banff or toronto' is the wordplay.
'in' indicates a hidden word.
'FORT' is hidden within 'banff or toronto'.
(Other definitions for fort that I've seen before include "& 22 US Army post" , "US gold reserves are at - Knox" , "Garrison" , "Military post in the old West" , "Strategic position" .)