Herb for Mr Fawlty (5)
I believe the answer is:
basil
I believe this clue is a triple definition!
'herb' is the first definition.
(basil is a herb)
'for mr' is the second definition.
'fawlty' is the third definition.
(Basil Fawlty of the sitcom Fawlty Towers)
(Other definitions for basil that I've seen before include "Name of male" , "Culinary plant" , "Herb; forename" , "Herb; man's name" , "A herb; --- Brush, Fawlty" .)