Like an understudy on stage? (6)

I believe the answer is:

acting

I believe this is a double definition.

'like an understudy' is the first definition.
(acting can mean working as a substitute)

'on stage?' is the second definition.
(I've seen this before)

(Other definitions for acting that I've seen before include "Temporarily doing another's duties" , "Stand-in" , "in a provisional role" , "Behaving in a certain way" , "Taking on duties temporarily" .)

I've seen this clue in The Telegraph.

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