Service, far up in the blue (3)

I believe the answer is:

raf

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'service' is the definition.
(Royal Air Force)

'far up in the blue' is the wordplay.
'far' can be anagrammed to 'RAF'.
However, I am not clear how the anagram is indicated.

Can you help me to learn more?

(Other definitions for raf that I've seen before include "Royal Air Force (abbr.)" , "Airforce of Great Britain" , "It fought Battle of Britain" .)

I've seen this clue in the Evening Standard.

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