It's nonsense some characters in Branagh's 'Othello' are upset (4)
I believe the answer is:
tosh
'it's nonsense' is the definition.
(tosh is a kind of nonsense)
'some characters in branagh's othello are upset' is the wordplay.
'some characters in' says the answer is hidden in the clue.
'are upset' says the letters should be written backwards.
'hsot' is hidden in the letters of 'branaghs othello'.
'hsot' reversed gives 'TOSH'.
(Other definitions for tosh that I've seen before include "Hooey" , "Nonsense (colloq.)" , "garbage'" , "Rubbish, nonsense" , "mate!" .)