Mice tunnels discovered - they were emitting light not caused by heat (11)

I believe the answer is:

luminescent

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'caused by heat' is the definition.
The answer and definition are not the same part of speech. However, past participle verbs and adjectives can sometimes mean the same thing.

'mice tunnels discovered they were emitting light not' is the wordplay.
'mice tunnels' anagrams to 'LUMINESCENT'.
Though, I am unsure how the anagram is indicated.

Can you help me to learn more?

(Other definitions for luminescent that I've seen before include "With light shining out" , "Giving off light" , "Emitting light without heat" .)

I've seen this clue in The Irish Times.

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