Possibly magical symbol that has left Potter unexcited? (4)

I believe the answer is:

rune

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

'possibly magical symbol' is the definition.
'rune' can be an answer for 'symbol' (rune is a kind of symbol). I'm not certain of the 'possibly magical' bit.

'has left potter unexcited?' is the wordplay.
'RUNE' is hidden within the letters.
But, I am not sure how the hidden word is indicated.

'that' is the link.

Can you help me to learn more?

(Other definitions for rune that I've seen before include "Ancient symbol" , "Spell" , "Mysterious character" , "Letter of an ancient Germanic alphabet" , "Early symbol used in carvings" .)

I've seen this clue in The Times.

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