Support at Covent Garden for Shaw's play? (3,5,4)

I believe the answer is:

the apple cart

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'play?' is the definition.
(I've seen this before)

I don't understand how the rest of the clue works.

(Other definitions for the apple cart that I've seen before include "Play by G.B. Shaw" , "George Bernard Shaw play" , "What spoiler upsets" , "Play by G. B. Shaw" , "Shaw play (that caused 6?)" .)

I've seen this clue in The Times.

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