'Mighty Mouse' -- is Mickey taking part? (7)

I believe the answer is:

seismic

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'mighty' is the definition.
Both the definition and answer are adjectives. Maybe there's an association between them I don't understand?

'mouse is mickey taking part?' is the wordplay.
'taking part?' indicates the answer is hidden within the clue.
'SEISMIC' is hidden in the letters of 'mouse is mickey'.

Can you help me to learn more?

(Other definitions for seismic that I've seen before include "Of earth tremors" , "massive" , "Caused by an earthquake" , "Resulting from earthquakes" , "Earthshaking" .)

I've seen this clue in The Telegraph.

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