Clot Charlie ruled out (6)
I believe the answer is:
curdle
'clot' is the definition.
(synonyms)
'charlie ruled out' is the wordplay.
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'ruled' is an anagram of 'urdle'.
'c'+'urdle'='CURDLE'
(Other definitions for curdle that I've seen before include "Of milk, turn sour and form thick substance" , "Cause (milk) to coagulate" , "Go bad or sour" , "Go bad -- turn from liquid into solids" , "cause milk problem" .)