Coolness under pressure (5)
I believe the answer is:
poise
'coolness under pressure' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for poise that I've seen before include "Sang-froid" , "Grace; equilibrium" , "Dignity; equilibrium" , "Balance; composure" , "Coolness and composure under strain" .)