Sanctify, oddly eyeing a day for pranks (9)

I believe the answer is:

halloween

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'a day for pranks' is the definition.
I can't tell whether this defines the answer.

'sanctify oddly eyeing' is the wordplay.
'sanctify' becomes 'hallow' (synonyms).
'oddly' indicates alternate letters (letters in the odd-numbered positions are used).
The alternating letters of 'eyeing' are 'een'.
'hallow'+'een'='HALLOWEEN'

Can you help me to learn more?

(Other definitions for halloween that I've seen before include "special night" , "Last night in October" , "Night of October thirty-first" , "Trick or treat time" , "Light-in-pumpkin festival" .)

I've seen this clue in the Sydney Morning Herald.

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