Shows brilliance, perhaps, in Donegal? (6)

I believe the answer is:

lustre

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

'shows brilliance' is the definition.
'lustre' can be an answer for 'brilliance' (I've seen this before). I am not sure about the 'shows' bit.

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for lustre that I've seen before include "Rustle up the sheen" , "Gentle sheen, soft glow" , "Glory; soft glow" , "Brilliant quality in a material, porcelain, etc" , "effect of reflected light" .)

I've seen this clue in The Irish Times.

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