Swoops down to grab papers and causes disunity (7)
I believe the answer is:
divides
'causes disunity' is the definition.
Although both the answer and definition are verbs in their -s form, I cannot see how they can define each other.
'swoops down to grab papers' is the wordplay.
'swoops down' becomes 'dives' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'to grab' means one lot of letters goes inside another.
'papers' becomes 'ID' (short for identification papers).
'dives' going around 'id' is 'DIVIDES'.
'and' is the link.
Can you help me to learn more?
(Another definition for divides that I've seen is " Separates into portions".)