Heat, sweeten and spice; finished, then contemplate (4,4)
I believe the answer is:
mull over
'contemplate' is the definition.
(I know that contemplate can be written as mull over)
'heat sweeten and spice finished' is the wordplay.
I cannot really understand how this works, but
'sweeten' could be 'mull' (mulling is a kind of sweetening) and 'mull' is present in the answer.
'finished' could be 'over' (over can mean finished or ended) and 'over' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'then' acts as a link.
Can you help me to learn more?
(Other definitions for mull over that I've seen before include "Ruminate, ponder" , "Consider" .)