Crossword Genius

Inception filmed here? (5)

Ross

I believe the answer is:

onset

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

This clue might be a double definition.

'inception' is the first definition.
(I've seen this in another clue)

'filmed here?' is the second definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.

Can you help me to learn more?

(Other definitions for onset that I've seen before include "Advent" , "Kick-off" , "Start, beginning" , "Beginning or early stages" , "Cast stone in attack" .)

I've seen this clue in The Independent.
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