Crossword Genius

Ultrafine service? (3)

Ross

I believe the answer is:

raf

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

'service?' is the definition.

'ultrafine' is the wordplay.
'RAF' is hidden within the letters.
But, I am unsure how the hidden word is indicated.

Can you help me to learn more?

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

I've seen this clue in the Evening Standard.
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