Barman's shake Mr Bean regularly sent back (6)
I believe the answer is:
wagner
'barman's' is the definition.
(composer Richard Wagner wrote bars of music)
'shake mr bean regularly sent back' is the wordplay.
'shake' becomes 'wag' (synonyms).
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'sent back' is a reversal indicator.
'mr'+'bean'='mrbean'
The alternating letters of 'mrbean' are 'ren'.
'ren' backwards is 'ner'.
'wag'+'ner'='WAGNER'
(Other definitions for wagner that I've seen before include "We rang up the composer" , "Richard . . . . . . composer of 'The Flying Dutchman' and 'Lohengrin'" , "German cycle-maker" , "Composer of ''The Flying Dutchman'' etc" , ""The Ring of the Nibelung" composer" .)