All yours open initially outwards yet ours upwards (4,2,3)
I believe the answer is:
over to you
'all yours' is the definition.
I know nothing about this answer so I cannot judge whether this works.
'open initially outwards yet ours upwards' is the wordplay.
'open' becomes 'overt' (associated in meaning).
'initially' suggests taking the first letters.
The first letters of 'outwards yet ours upwards' is 'oyou'.
'overt'+'oyou'='OVER TO YOU!'
Can you help me to learn more?
(Other definitions for over to you that I've seen before include "Your turn to act, I've done my bit" , "Your turn now, I've done my share" , "Your turn next - I've done my stint" , "Words to delegate" .)