Obey guards united by lives changed by force (12)

I believe the answer is:

compulsively

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'obey guards united by lives changed by force' is the definition.
I can't tell whether this definition defines the answer.

'obey guards united by lives changed' is the wordplay.
'obey' becomes 'comply' (complying is a kind of obeying).
'guards' indicates putting letters inside (inserted letters are guarded).
'united by' becomes 'u' (as in Man U, English football team. I am not sure about the 'by' bit.).
'changed' indicates anagramming the letters.
'lives' with letters rearranged gives 'lsive'.
'u'+'lsive'='ulsive'
'comply' going around 'ulsive' is 'COMPULSIVELY'.

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I've seen this clue in The Guardian.

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