Superhero's attendant (6)
I believe the answer is:
batman
I believe this is a double definition.
'superhero's' is the first definition.
(I have seen 'Comic superhero ' mean 'batman' so perhaps 'superhero' could also mean 'batman')
'attendant' is the second definition.
(batman is a kind of attendant)
(Other definitions for batman that I've seen before include "Comic strip character" , "Army servant - comic character" , "Cartoon hero or officer's servant" , "Comic book hero with Robin as a sidekick" , "'British military orderly, with Robin as a sidekick? (6)'" .)