A quick drop before opening time? (4,4)

I believe the answer is:

free fall

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'a quick drop before opening time?' is the definition.
(fast descent before the parachute opens)

'a quick drop' is the wordplay.
'a quick' becomes 'free' (I can't justify this - if you can you should believe this answer much more).
'drop' becomes 'fall' (synonyms).
'free'+'fall'='FREE FALL'

Can you help me to learn more?

(Other definitions for free fall that I've seen before include "Drop with parachute unopened" , "Rapid descent (before parachute opens, for example)" , "Uncontrolled descent" , "Motion under gravity" , "skydiving practice?" .)

I've seen this clue in The Telegraph.

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