Deliberately lose boxing match – no longer bold – waste (5,3)
I believe the answer is:
throw out
'waste' is the definition.
(I know that waste is a kind of the throw out)
'deliberately lose boxing match no longer bold' is the wordplay.
'deliberately lose' becomes 'throw' (I've seen this before).
'boxing match' becomes 'bout' (bout can mean a boxing match).
'no longer' is a deletion indicator.
'bold' becomes 'b' (abbreviation).
'bout' with 'b' removed is 'out'.
'throw'+'out'='THROW OUT'
(Other definitions for throw out that I've seen before include "Eject or discard as rubbish" , "Discard; confuse" , "Reject" , "Eject or evict" , "Expel - disconcert" .)