Artist featured in ridiculously mad play (5)
I believe the answer is:
drama
'play' is the definition.
(I know that play can be written as drama)
'artist featured in ridiculously mad' is the wordplay.
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'featured in' indicates putting letters inside.
'ridiculously' indicates an anagram (I've seen this in other clues).
'mad' is an anagram of 'dma'.
'ra' put into 'dma' is 'DRAMA'.
(Other definitions for drama that I've seen before include "Play - big emotional scene" , "Theatrical play" , "Stage play, may be exciting" , "Stage production" , "Acting" .)