Theatre gates open (5)

I believe the answer is:

stage

I'm a little stuck... Click here to teach me more about this clue!

'theatre' is the definition.
(I know that stage is a type of theatre)

'gates open' is the wordplay.
'gates' anagrams to 'STAGE'.
However, I am not sure how the anagram is indicated.

Can you help me to learn more?

(Other definitions for stage that I've seen before include "Platform for actors" , "Acting area" , "Section (of journey)" , "Podium" , "Acting platform; coach" .)

I've seen this clue in The Irish Independent.

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