Give another title to nobleman erroneously, some reflected (6)
I believe the answer is:
rename
'give another title to' is the definition.
'nobleman erroneously some reflected' is the wordplay.
'some' indicates the answer is hidden within the clue.
'reflected' says the letters should be written in reverse.
'emaner' can be found hidden inside 'nobleman erroneously'.
'emaner' reversed gives 'RENAME'.
(Other definitions for rename that I've seen before include "Alter title of" , "Rechristen" , "Call again" , "Give a new title to" , "Confer new appellation of meaner sort" .)