Plenitude (9)
I believe the answer is:
abundance
'plenitude' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for abundance that I've seen before include "great deal" , "Plentiful supply" , "Profusion, richness" , "Ample sufficiency or great plenty." , "Large amount, sometimes more than is needed" .)