Warm up; preliminary round (4)
I believe the answer is:
heat
I believe this is a double definition.
'warm up' is the first definition.
(I've seen this in another clue)
'preliminary round' is the second definition.
(I've seen this in another clue)
(Other definitions for heat that I've seen before include "Cook" , "Toast" , "Hotness" , "It's measured in therms" , "Warm up" .)