It's time to split up gold-plated cube (5)
I believe the answer is:
adieu
'it's time to split up' is the definition.
I can't judge whether this defines the answer.
'gold-plated cube' is the wordplay.
'gold' becomes 'au' (Au is the chemical symbol for gold).
'plated' indicates putting letters inside.
'cube' becomes 'die' (die is a kind of cube).
'au' placed around 'die' is 'ADIEU'.
Can you help me to learn more?
(Other definitions for adieu that I've seen before include "Goodbye in France" , "Comment on leaving" , "Farewel" , "the last word in Paris" , "Fare thee well!" .)