Police officer starts to scrutinise criminal's record (4)
I believe the answer is:
disc
'record' is the definition.
(eg a CD, compact disc)
'police officer starts to scrutinise criminal's' is the wordplay.
'police officer' becomes 'di' (detective inspector).
'starts to' says to take the initial letters.
The first letters of 'scrutinise criminals' is 'sc'.
'di'+'sc'='DISC'
(Other definitions for disc that I've seen before include "Layer of cartilege between vertebrae" , "Body without limbs" , "One of 33, 45 or 78?" , "Flat round plate" , "Capital of India" .)