Record some police about to arrest son (4)
I believe the answer is:
disc
'record' is the definition.
('disc' can be a synonym of 'record')
'some police about to arrest son' is the wordplay.
'some police' becomes 'cid'.
'about' shows that the letters should be reversed in order.
'to arrest' is an insertion indicator.
'son' becomes 's'.
'cid' reversed gives 'dic'.
'dic' enclosing 's' is 'DISC'.
(Other definitions for disc that I've seen before include "One of 33, 45 or 78?" , "Old record" , "Compact ---; slipped ---" , "Sound recording" , "Layer of cartilege between vertebrae" .)