Movement of territory particle (6)
I believe the answer is:
action
'movement' is the definition.
(I've seen this in another clue)
'territory particle' is the wordplay.
'territory' becomes 'act' (I can't explain this - if you can you should give a lot more credence to this answer).
'particle' becomes 'ion' (I've seen this in another clue).
'act'+'ion'='ACTION'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for action that I've seen before include "skirmish" , "Operation - lawsuit" , "Director's cue?" , "''. . . . . . speaks louder than words'' (6)" , "Deed - lawsuit - battle" .)