Batman initially held by wrongly arrested Robin (9)
I believe the answer is:
redbreast
'robin' is the definition.
(synonyms)
'batman initially held by wrongly arrested' is the wordplay.
'initially' suggests taking the first letters.
'held by' indicates putting letters inside.
'wrongly' indicates an anagram (I've seen this in other clues).
The initial letter of 'batman' is 'b'.
'arrested' with letters rearranged gives 'redreast'.
'b' inserted within 'redreast' is 'REDBREAST'.
(Other definitions for redbreast that I've seen before include "One tweets" , "Bird" , "Type of robin" , "Flapper" .)