Lost, new hero impossible to find? (7)
I believe the answer is:
nowhere
'impossible to find?' is the definition.
(as in 'nowhere to be found')
'lost new hero' is the wordplay.
'lost' indicates anagramming the letters.
'new'+'hero'='newhero'
'newhero' anagrammed gives 'NOWHERE'.
(Other definitions for nowhere that I've seen before include "... and the rest ____"" , "insignificant place?" , "News from - (William Morris)" , "Utopia" , "Out of the running" .)