Both sides in final have gone quickly (5)
I believe the answer is:
flown
'gone quickly' is the definition.
'flown' can be an answer for 'gone' (I've seen this before). I'm not certain of the 'quickly' bit.
'both sides in final have' is the wordplay.
'both sides in' means to remove the middle letters (only the side letters remain).
'have' becomes 'own' (to have something is to own it).
'final' with its middle removed is 'fl'.
'fl'+'own'='FLOWN'
Can you help me to learn more?
(Other definitions for flown that I've seen before include "Disappeared" , "(Time has) gone quickly" .)