Pot red by mistake - it's too much (2,4)
I believe the answer is:
de trop
'too much' is the definition.
(I've seen this in another clue)
'pot red by mistake' is the wordplay.
'by mistake' indicates anagramming the letters.
'pot'+'red'='potred'
'potred' is an anagram of 'DE TROP'.
'it's' is the link.
(Other definitions for de trop that I've seen before include "not to drink too much" , "In the way, unwanted as in France" , "Superfluous (French)" , "Excessive - not wanted" , "'Unreasonable or unwelcome (2,4)'" .)