Crossword Genius

Is humanitarian, but makes a leftist angry (3,5)

Ross

I believe the answer is:

red cross

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'is humanitarian but' is the definition.
I can't tell whether this definition defines the answer.

'a leftist angry' is the wordplay.
'a leftist' becomes 'red' (red can informally mean communist).
'angry' becomes 'cross' (cross can mean annoyed or angry).
'red'+'cross'='RED-CROSS'

'makes' is the link.

Can you help me to learn more?

(Other definitions for red cross that I've seen before include "flag" , "International relief organisation" , "International oranisation for treatment of wounded in war" , "International movement" , "Medical group" .)

I've seen this clue in the Evening Standard.
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