Fantastic comedy film subject inspiring poor over time (9)

I believe the answer is:

brilliant

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

'fantastic' is the definition.

'inspiring poor over time' is the wordplay.
'inspiring' is an insertion indicator.
'poor' becomes 'ill' (I've seen this in another clue).
'over time' becomes 'briant' (I can't justify this - if you can you should believe this answer much more).
'ill' going within 'briant' is 'BRILLIANT'.

'comedy film subject' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.

Can you help me to learn more?

(Other definitions for brilliant that I've seen before include "Of surpassing excellence" , "Of outstanding ability" , "Vivid; clever" , "Very bright; marvellous" , "Magnificent" .)

I've seen this clue in The Times.

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