One old-fashioned hero (4)
I believe the answer is:
idol
'hero' is the definition.
(thesaurus)
'one old-fashioned' is the wordplay.
'one' becomes 'i' (Roman numeral**).
'fashioned' indicates an anagram.
'old' with letters rearranged gives 'dol'.
'i'+'dol'='IDOL'
(Other definitions for idol that I've seen before include "False god" , "Object of false worship" , "Something worshipped" , "Admired figure" , "Subject of adoration, may be graven" .)