Showman is more rapid, endlessly shuffling (10)
I believe the answer is:
impresario
'showman' is the definition.
('impresario' can be a synonym of 'showman')
'is more rapid endlessly shuffling' is the wordplay.
'endlessly' means to remove the last letter.
'shuffling' indicates anagramming the letters.
'is'+'more'+'rapid'='ismorerapid'
'ismorerapid' with its final letter removed is 'ismorerapi'.
'ismorerapi' anagrammed gives 'IMPRESARIO'.
(Other definitions for impresario that I've seen before include "Producer of performing arts" , "Perhaps the Met's manager" , "Entertainer" , "Theatre promoter" , "Theatrical manager" .)