The method of a showman (3)
I believe the answer is:
how
'the method' is the definition.
(I've seen this in another clue)
'of a showman' is the wordplay.
'of' indicates the answer is hidden within the clue.
'HOW' is hidden within 'showman'.
(Other definitions for how that I've seen before include "By what means?" , "See 16" , "Who (anag.)" , "In what way?" , "In what manner or method?" .)