Informal time for kiss identified (7)

I believe the answer is:

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'informal' is the definition.
Both the definition and answer are adjectives. Maybe you can see an association between them that I don't see?

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

Can you help me to learn more?

(Other definitions for related that I've seen before include "Told; akin" , "were sympathetic" , "Connected by blood or marriage" , "of one family" , "Like family members" .)

I've seen this clue in The Independent.

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