American politician's one foul trick (6)
I believe the answer is:
neocon
'american politician's' is the definition.
(US term for a neoconservative)
'one foul trick' is the wordplay.
'foul' indicates an anagram.
'trick' becomes 'con' (a con is a fraud or trick).
'one' is an anagram of 'neo'.
'neo'+'con'='NEOCON'
(Other definitions for neocon that I've seen before include "Someone advocating a new form of democratic capitalism" , "Traditionalist" , "politician on the right" , "Right-winger" , "A supporter of the policies of President George Bush? (abbr)" .)