Learned English: ill-mannered about it (7)
I believe the answer is:
erudite
'learned' is the definition.
(synonyms)
'english ill-mannered about it' is the wordplay.
'english' becomes 'E' (abbreviation).
'ill-mannered' becomes 'rude' (synonyms).
'about' is an insertion indicator.
'rude' placed around 'it' is 'rudite'.
'e'+'rudite'='ERUDITE'
(Other definitions for erudite that I've seen before include "'Learned, knowledgeable (7)'" , "Rude tie (anag.)" , "Rue diet for the learned" , "Learned and scholarly" , "Showing profound knowledge" .)