No robe for a king (6)

I believe the answer is:

oberon

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

'for a king' is the definition.
(I've seen this before)

'no robe' is the wordplay.
'no robe' anagrams to 'OBERON'.
However, I am not clear how the anagram is indicated.

Can you help me to learn more?

(Other definitions for oberon that I've seen before include "Satellite" , "Titania's husband" , "Shakespeare's fairy king" , "Titania's king" , "King of the fairies (AMND)" .)

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

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