Evil one cruel if disturbed (7)

I believe the answer is:

lucifer

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'evil one' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.

'cruel if disturbed' is the wordplay.
'disturbed' indicates anagramming the letters (the order of letters is disturbed).
'cruel'+'if'='cruelif'
'cruelif' with letters rearranged gives 'LUCIFER'.

Can you help me to learn more?

(Other definitions for lucifer that I've seen before include "Rebellious angel; a match" , "Prince of Darkness" , "Satan, the Dark Angel" , "Devil - match!" , "Satan, the Devil" .)

I've seen this clue in The Sun.

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