Lose one's cool in 2 (4)
I believe the answer is:
snap
'lose one's cool' is the definition.
(I've seen this in another clue)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for snap that I've seen before include "Speak irritably; photo" , "Break suddenly and cleanly" , "Break suddenly with cracking sound" , "Snarl at - photograph" , "Break like informal photo" .)