Gielgud as Hamlet shows style (4)
I believe the answer is:
dash
'style' is the definition.
(I know that style can be written as dash)
'gielgud as hamlet shows' is the wordplay.
'shows' says the answer is hidden in the clue.
'DASH' can be found hidden inside 'gielgud as hamlet'.
(Other definitions for dash that I've seen before include "Hyphen - bother!" , "Elan; run" , "style" , "rats" , "Smash - bother! - make a run for it" .)