No police officer agrees (4)
I believe the answer is:
nods
'agrees' is the definition.
(I've seen this before)
'no police officer' is the wordplay.
'police officer' becomes 'ds' (short for detective sergeant).
'no'+'ds'='NODS'
(Other definitions for nods that I've seen before include "Non-verbal indications of assent" , "Indicates assent" , "Shows assent" , "is about to crash?" , "Signals assent" .)