Miso soup finally eaten, he says (5)
I believe the answer is:
simon
'he says' is the definition.
(I've seen this in another clue)
'miso soup finally eaten' is the wordplay.
'soup' indicates anagramming the letters.
'finally' says to take the final letters.
The last letter of 'eaten' is 'n'.
'miso' anagrammed gives 'simo'.
'simo'+'n'='SIMON'
(Other definitions for simon that I've seen before include "Bolivar, de Montfort, Callow or Cowell?" , "disciple" , "Man's name" , "Peter (NT)" , "He's simple in rhyme" .)