Kept cool (8)
I believe the answer is:
reserved
This clue is a double definition.
'kept' is the first definition.
(reserving is a kind of keeping)
'cool' is the second definition.
(I've seen this before)
(Other definitions for reserved that I've seen before include "Set aside; reticent" , "Retiring" , "Held back, set aside" , "without emotion" , "unforthcoming" .)