Excess supply (4)
I believe the answer is:
glut
'excess supply' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for glut that I've seen before include "Overabundance" , "A surfeit as of crops" , "Excessively abundant supply" , "An excessive supply, maybe on the market" , "Excess, surfeit" .)