Reptile working in Canada corruptly (8)
I believe the answer is:
anaconda
'reptile' is the definition.
(anaconda is a kind of reptile)
'working in canada corruptly' is the wordplay.
'working' becomes 'on' (on can mean working or activated).
'in' indicates putting letters inside.
'corruptly' is an anagram indicator.
'canada' anagrammed gives 'anacda'.
'on' inserted inside 'anacda' is 'ANACONDA'.
(Other definitions for anaconda that I've seen before include "Large South American snake" , "Snake of the boa family" , "Boa constrictor" , "cold-blooded killer" , "Huge South American snake" .)