Too much left in the intestine (4)
I believe the answer is:
glut
'too much' is the definition.
(I've seen this before)
'left in the intestine' is the wordplay.
'left' becomes 'l' (common abbreviation).
'in the' indicates putting letters inside.
'intestine' becomes 'gut' ('gut' can be a synonym of 'intestine').
'l' placed into 'gut' is 'GLUT'.
(Other definitions for glut that I've seen before include "stuff" , "Satiate" , "Flood" , "A surplus or excess" , "Overabundance" .)