Banner includes monarch (4)
I believe the answer is:
anne
'monarch' is the definition.
(Queen Anne, 18th-century queen)
'banner includes' is the wordplay.
'includes' indicates a hidden word.
'ANNE' can be found hidden inside 'banner'.
(Other definitions for anne that I've seen before include "Henry's second" , "Queen's name" , "Boleyn or Hathaway, say" , "Prince Charles's sister" , "Shakespeare's wife's name" .)