Can such life be spoilt by getting out of line? (7)

I believe the answer is:

married

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'out of line?' is the definition.
Both the answer and definition are adjectives. Perhaps there's a link between them I don't understand?

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for married that I've seen before include "Wedded" , "Spliced" , "Hitched" , "Espoused" , "Not single" .)

I've seen this clue in the Evening Standard.

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