Charlie spots collision (5)
I believe the answer is:
crash
'collision' is the definition.
(crash is a kind of collision)
'charlie spots' is the wordplay.
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'spots' becomes 'rash' (I've seen this before).
'c'+'rash'='CRASH'
(Other definitions for crash that I've seen before include "Car accident" , "Planned quickly for emergency" , "Economic collapse" , "failure" , "(Of shares) fall suddenly by a great amount" .)