Shadow cast out in Burma (5)

I believe the answer is:

umbra

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

'shadow' is the definition.
(I know that umbra is a type of shadow)

'cast out in burma' is the wordplay.
'burma' anagrams to 'UMBRA'.
But, I am unsure how this is indicated.

Can you help me to learn more?

(Other definitions for umbra that I've seen before include "Burma (anag.)" , "dark place" , "Black spot" , "Region of shadow" , "Dark shadow cast by earth in eclipse" .)

I've seen this clue in The Globe and Mail.

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