Swag hidden in Waterloo terminus (4)
I believe the answer is:
loot
'swag' is the definition.
(I know that swag can be written as loot)
'hidden in waterloo terminus' is the wordplay.
'hidden in' indicates the answer is hidden within the clue.
'LOOT' is hidden within 'waterloo terminus'.
(Other definitions for loot that I've seen before include "rifle" , "Booty, spoils" , "Stolen goods" , "Booty; sack" , "Orton play; money" .)