Great German workers’ party nevertheless to be sold short (9)
I believe the answer is:
beethoven
'great german' is the definition.
'workers' party nevertheless to be sold short' is the wordplay.
'workers' party' becomes 'bee' (communal event for doing a particular type of work).
'nevertheless' becomes 'tho' (informal spelling of 'though').
'to be sold' becomes 'vend' (to vend could historically mean to be sold).
'short' means to remove the last letter.
'vend' with its last letter taken off is 'ven'.
'bee'+'tho'+'ven'='BEETHOVEN'
(Other definitions for beethoven that I've seen before include "Ludwig van . . . . . . . . ., immortal German composer 1770-1827 (9)" , "He be no vet, this German composer" , "source of bars?" , "Ludwig van .. . . . . . . ., great German composer" , "German barman" .)