Mixes up seasonal posts - openings go begging (10)

I believe the answer is:

interlaces

I'm a little stuck... Click here to teach me more about this clue!

'mixes' is the definition.
The definition and answer can be both to do with contact as well as being verbs in their -s form.
Perhaps they are linked in a way I don't understand?

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

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