Serious disloyalty from maverick senator (7)

I believe the answer is:

treason

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'serious disloyalty' is the definition.
'treason' can be an answer for 'disloyalty' (treason is a kind of disloyalty). I am unsure of the 'serious' bit.

'maverick senator' is the wordplay.
'maverick' indicates anagramming the letters.
'senator' with letters rearranged gives 'TREASON'.

'from' acts as a link.

Can you help me to learn more?

(Other definitions for treason that I've seen before include "Lese-majesty" , "Perfidy" , "Betrayal (of one's country)" , "Crime of national betrayal" , "Betrayal of one's nation" .)

I've seen this clue in The Guardian.

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