Warms up for the opening races (5)
I believe the answer is:
heats
This could be a double definition.
'warms up' is the first definition.
(I've seen this in another clue)
'opening races' is the second definition.
'heats' can be an answer for 'races' (I've seen this before). I'm unsure of the 'opening' bit.
'for the' acts as a link.
Can you help me to learn more?
(Other definitions for heats that I've seen before include "Warms up for the preliminary races" , "Makes hot or warm" , "Haste (anag.)" , "Eliminating rounds in a contest" , "Eliminating rounds of a race" .)