Collision of the cool-headed and hot-headed (5)
I believe the answer is:
crash
'collision' is the definition.
(I know that collision can be written as crash)
'the cool-headed and hot-headed' is the wordplay.
'the cool-headed' becomes 'c' (this might be a standard abbreviation I've not previously seen).
'and' says to put letters next to each other.
'hot-headed' becomes 'rash' (I've seen this before).
'c'+'rash'='CRASH'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for crash that I've seen before include "Disastrous market fall" , "Car accident" , "Economic collapse" , "Dramatic fall" , "Bang" .)