Greek boy seen after no-one goes west (6)
I believe the answer is:
ionian
'greek' is the definition.
(I know that Ionian is a type of greek)
'boy seen after no-one goes west' is the wordplay.
'boy' becomes 'ian' (man's name).
'seen after' means one lot of letters go next to another.
'one' becomes 'i' (Roman numeral).
'goes west' is a reversal indicator.
'no'+'i'='noi'
'noi' in reverse letter order is 'ion'.
'ian' put after 'ion' is 'IONIAN'.
(Other definitions for ionian that I've seen before include "from Greek Islands" , "Sea between Greece and Sicily" , "Sea between southern Italy and western Greece" , "Sea between Greece and south Italy" .)