Scheme of theft by Tories (10)
I believe the answer is:
conspiracy
'scheme' is the definition.
(I've seen this before)
'theft by tories' is the wordplay.
'theft' becomes 'piracy' (piracy is a kind of theft).
'by' means one lot of letters go next to another.
'tories' becomes 'cons' (I've seen this in other clues).
'piracy' put after 'cons' is 'CONSPIRACY'.
'of' acts as a link.
(Other definitions for conspiracy that I've seen before include "Plot" , "scheme" , "Secret plan" , "This is intriguing" , "that involves plotting" .)