Angry enough to change sides? (5)

I believe the answer is:

cross

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'angry' is the definition.
(cross can mean annoyed or angry)

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

(Other definitions for cross that I've seen before include "Pass from the wing to the penalty area" , "X" , "religious symbol" , "Go to the other side" , "See 2" .)

I've seen this clue in the Evening Standard.

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