Squad adopts local courtesy? (9)
I believe the answer is:
politesse
'courtesy?' is the definition.
(I know that politesse is a type of courtesy)
'squad adopts local' is the wordplay.
'squad' becomes 'posse' (I've seen this in another clue).
'adopts' is an insertion indicator.
'local' becomes 'lite' (I can't justify this - if you can you should give a lot more credence to this answer).
'posse' going around 'lite' is 'POLITESSE'.
Can you help me to learn more?
(Other definitions for politesse that I've seen before include "Etiquette" , "formal courtesy" , "Chivalry" .)