Twilight Zone at first featured in homework? That's silly (5)

I believe the answer is:

ditzy

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'silly' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.

'twilight zone at first featured in homework?' is the wordplay.
'at first' suggests taking the first letters.
'featured in' is an insertion indicator.
'homework?' becomes 'diy' (DIY is work done on your home).
The initial letters of 'twilight zone' is 'tz'.
'tz' inserted within 'diy' is 'DITZY'.

'that's' acts as a link.

Can you help me to learn more?

I've seen this clue in The Times.

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