Greek character's collared by drunk philosopher (7)
I believe the answer is:
sophist
'philosopher' is the definition.
(I know that Sophist is a type of philosopher)
'greek character's collared by drunk' is the wordplay.
'greek character's' becomes 'phi's' (letter from the Greek alphabet).
'collared by' is an insertion indicator (I've seen this in other clues).
'drunk' becomes 'sot' (sot can mean a drunken person).
'phis' placed within 'sot' is 'SOPHIST'.
(Other definitions for sophist that I've seen before include "One using clever but fallacious arguments" , "One given to specious reasoning" , "Clever but fallacious reasoner" , "one might plausibly argue" , "One using clever but wrong arguments" .)