Moving camera captures old police force in Night of the Long Knives (8)
I believe the answer is:
massacre
'force in night of the long knives' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
'moving camera captures old police' is the wordplay.
'moving' is an anagram indicator.
'captures' is an insertion indicator.
'old police' becomes 'ss' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'camera' anagrammed gives 'maacre'.
'maacre' going around 'ss' is 'MASSACRE'.
Can you help me to learn more?
(Other definitions for massacre that I've seen before include "Complete defeat" , "Overwhelming defeat" , "Kill" , "Slaughter of large number of people" , "Widespread killing" .)