Glut, surfeit (13)
I believe the answer is:
overabundance
I believe this clue is a double definition.
'glut' is the first definition.
(I've seen this before)
'surfeit' is the second definition.
(synonyms)
(Other definitions for overabundance that I've seen before include "Excessive quantity" , "Excess quantity" , "Glut" , "Surplus, excess" .)