Speed in heats, uncommon (5)
I believe the answer is:
haste
'speed' is the definition.
(haste is a kind of speed)
'heats uncommon' is the wordplay.
'uncommon' indicates anagramming the letters.
'heats' anagrammed gives 'HASTE'.
'in' is the link.
(Other definitions for haste that I've seen before include "Inconsiderate speed" , "Speediness or rush" , "impetuosity" , "Expedition" , "velocity" .)