I'd look up to this hero (4)
I believe the answer is:
idol
'this hero' is the definition.
(thesaurus)
'i'd look up' is the wordplay.
'look' becomes 'lo'.
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'lo' reversed gives 'ol'.
'id'+'ol'='IDOL'
'to' acts as a link.
(Other definitions for idol that I've seen before include "Figure of worship" , "Graven image or worshipped person" , "One much admired" , "Honoured figure" , "A graven image, or a hero" .)