Six iron, say, oddly unpractical (9)
I believe the answer is:
visionary
'unpractical' is the definition.
(thesaurus)
'six iron say oddly' is the wordplay.
'six' becomes 'vi' (roman numeral).
'oddly' is an anagram indicator.
'iron'+'say'='ironsay'
'ironsay' with letters rearranged gives 'sionary'.
'vi'+'sionary'='VISIONARY'
(Other definitions for visionary that I've seen before include "impracticable" , "Prophetic" , "Idealistic" , "Seer" .)