Opening in fact an inadequate window (8)

I believe the answer is:

fanlight

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'window' is the definition.
(I know that fanlight is a type of window)

'opening in fact an inadequate' is the wordplay.
'opening in' suggests taking the first letters.
'inadequate' becomes 'light' (I am not sure about this - if you are sure you should believe this answer much more).
The first letter of 'fact' is 'f'.
'f'+'an'+'light'='FANLIGHT'

Can you help me to learn more?

(Other definitions for fanlight that I've seen before include "kind of window" , "It enables us to see" , "Thin flag (anag.)" , "elevated aperture" , "Small window" .)

I've seen this clue in The Telegraph.

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