Fiery temperament (5)
I believe the answer is:
blood
'fiery temperament' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for blood that I've seen before include "Oxygen-carrying liquid" , "It contains plasma and platelets" , "Kinship; temperament" , "It's said to be thicker than water" , "Fluid in veins" .)