Completed insurance, shelling out $100 (4)
I believe the answer is:
over
'completed' is the definition.
(synonyms)
I can't explain the remainder of the clue.
(Other definitions for over that I've seen before include "Finished -- as a remainder" , "Bout of six bowls in cricket" , "Finished like bowling session" , "Higher than; finished" , "A bowler's round in cricket" .)