Stopper clears out rapidly, kicking first of all (4)
I believe the answer is:
cork
'stopper' is the definition.
(cork is a kind of stopper)
'clears out rapidly kicking first of all' is the wordplay.
'first of all' suggests taking the first letters.
The initial letters of 'clears out rapidly kicking' is 'CORK'.
(Other definitions for cork that I've seen before include "Bung for a bottle" , "stop" , "Bottle-stopper for a southern city" , "It's needed for a bottle of wine" , "Why wine can't be accessed" .)