Large liver OK cooked, but too much (8)
I believe the answer is:
overkill
'too much' is the definition.
('overkill' can mean excessive or too much)
'large liver ok cooked' is the wordplay.
'large' becomes 'l'.
'cooked' indicates an anagram.
'l'+'liver'+'ok'='lliverok'
'lliverok' with letters rearranged gives 'OVERKILL'.
'but' is the link.
(Other definitions for overkill that I've seen before include "Action far more drastic than necessary" , "Excessive action, armament" , "Hyperbole" , "Ridiculous excess" , "Surplus of capacity for task - sounds lethal" .)