Head of police called, revealing accident (5)
I believe the answer is:
prang
'accident' is the definition.
(I've seen this before)
'head of police called' is the wordplay.
'head of' indicates taking the first letters.
'called' becomes 'rang' ('ring' can be a synonym of 'call').
The initial letter of 'police' is 'p'.
'p'+'rang'='PRANG'
'revealing' acts as a link.
(Other definitions for prang that I've seen before include "Minor accident" , "Bomb attack" , "Possible argument with van" , "damage" , "Crash (informal)" .)