Greek leader implicated in new Euro fraud (5)
I believe the answer is:
rogue
'fraud' is the definition.
(thesaurus)
'greek leader implicated in new euro' is the wordplay.
'leader' suggests taking the first letters.
'implicated in' means one lot of letters goes inside another.
'new' is an anagram indicator.
The initial letter of 'greek' is 'g'.
'euro' is an anagram of 'roue'.
'g' going within 'roue' is 'ROGUE'.
(Other definitions for rogue that I've seen before include "Blackguard" , "Bad guy" , "Stray" , "Diverging from type" , "Fraud" .)