Barman: c-climb aboard (6)
I believe the answer is:
chopin
'barman' is the definition.
(Frederic Chopin, composer who 'bars' of music)
'c-climb aboard' is the wordplay.
'climb aboard' becomes 'hopin' ('hop in' is an instruction to board a vehicle).
'c'+'hopin'='CHOPIN'
(Other definitions for chopin that I've seen before include "Frederic . . . . . ., great Polish composer-pianist" , "his writing noted" , "Frederic ......, 19th century Polish composer, mostly for piano" , "See 10" , "Frederic -, nineteenth century Polish pianist and composer" .)