Old science magazine occupying fandom nightly (4)

I believe the answer is:

omni

'old science magazine' is the definition.
(20th-century science magazine)

'occupying fandom nightly' is the wordplay.
'occupying' says the answer is hidden in the clue (letters for the answer occupy part of the clue).
'OMNI' is hidden within 'fandom nightly'.

I've seen this clue in The Independent.

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