Makes meaning clear in Christmas verses? (7)

I believe the answer is:

decodes

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'makes meaning clear' is the definition.
Although both the answer and definition are verbs in their -s form, I can't understand how they can define each other.

'christmas verses?' is the wordplay.
'christmas' becomes 'dec' (Dec is short for December, the Christmas period).
'verses?' becomes 'odes' (I've seen this before).
'dec'+'odes'='DECODES'

'in' acts as a link.

Can you help me to learn more?

I've seen this clue in The Guardian.

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