To the French, terrible bilge is readable! (7)
I believe the answer is:
legible
'readable' is the definition.
(similar in meaning)
'to the french terrible bilge' is the wordplay.
'to the french' becomes 'le' ('the' in French).
'terrible' indicates an anagram.
'bilge' anagrammed gives 'gible'.
'le'+'gible'='LEGIBLE'
'is' is the link.
(Other definitions for legible that I've seen before include "Clear enough to read" , "Well written" , "Capable to be read" , "possible to make out" , "Easy to read" .)