Protective wear Rachel half concealed on police force (6)
I believe the answer is:
helmet
'protective wear' is the definition.
(item that protects the head)
'rachel half concealed on police force' is the wordplay.
'half concealed' suggests halving the letters.
'on' is a charade indicator (letters next to each other).
'police force' becomes 'met' (short for Metropolitan Police Service).
'rachel' cut in half is 'hel'.
'hel'+'met'='HELMET'
(Other definitions for helmet that I've seen before include "Biker's headgear" , "Hard hat" , "Armour for the head" , "Police hat" , "Armor for the head" .)