Officer in company with the head of police (3)
I believe the answer is:
cop
'officer' is the definition.
(cop is a kind of officer)
'company with the head of police' is the wordplay.
'company' becomes 'co' (abbreviation).
'with' says to put letters next to each other.
'the head of' suggests taking the first letters.
The initial letter of 'police' is 'p'.
'co'+'p'='COP'
'in' acts as a link.
(Other definitions for cop that I've seen before include "Policeman (colloq.)" , "Policeman (sl)" , "catch" , "An American policeman" , "Policeman (slang)" .)