English in ridiculously heroic farewell (7)
I believe the answer is:
cheerio
'farewell' is the definition.
(I know that farewell can be written as cheerio)
'english in ridiculously heroic' is the wordplay.
'english' becomes 'e' (abbreviation).
'in' means one lot of letters goes inside another.
'ridiculously' indicates an anagram (I've seen this in other clues).
'heroic' anagrammed gives 'cherio'.
'e' placed inside 'cherio' is 'CHEERIO'.
(Other definitions for cheerio that I've seen before include "Informal farewell" , "Ta-ta" , "Farewell - drinking toast" , "British romance imprint" , "Expression used when leaving" .)