Leader of the Opposition hence organised military patrols (9)
I believe the answer is:
archenemy
'leader of the opposition' is the definition.
The definition suggests a singular noun which matches the answer.
'hence organised military patrols' is the wordplay.
I cannot quite see how this works, but
an anagram of 'hence' is 'chene' which is present in the answer.
'military' could be 'army' (the armed forces) and 'army' is present in the remaining letters.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for archenemy that I've seen before include "Main adversary" , "Cheery man can be greatest foe" , "Principal antagonist" , "Chief foe" , "Cheery man may be chief opponent" .)