Fall away, so give up (4,3)
I believe the answer is:
drop out
'give up' is the definition.
('drop out' can be a synonym of 'give up')
'fall away' is the wordplay.
'fall' becomes 'drop' (dropping is a kind of falling**).
'away' becomes 'out' ('out' can be a synonym of 'away').
'drop'+'out'='DROP-OUT'
'so' is the link.
(Other definitions for drop out that I've seen before include "Withdraw from activity" , "leave society?" , "cease being competitive" , "withdrawn student" , "Restart game" .)