Implement the return of the swag (4)
I believe the answer is:
tool
'implement' is the definition.
(I know that implement can be written as tool)
'return of the swag' is the wordplay.
'return of' is a reversal indicator.
'the swag' becomes 'loot' ('loot' can be a synonym of 'swag').
'loot' back-to-front is 'TOOL'.
'the' acts as a link.
(Other definitions for tool that I've seen before include "organ" , "Practical implement" , "Device used for work" , "Working instrument" , "Maybe saw" .)