“Farewell” here translated, one parting company (7)
I believe the answer is:
cheerio
'farewell' is the definition.
(cheerio is a kind of farewell)
'here translated one parting company' is the wordplay.
'translated' is an anagram indicator.
'one' becomes 'i' (Roman numeral).
'parting' is an insertion indicator (inserted letters split or part another word).
'company' becomes 'co' (abbreviation).
'here' anagrammed gives 'heer'.
'heer'+'i'='heeri'
'heeri' placed within 'co' is 'CHEERIO'.
(Other definitions for cheerio that I've seen before include "Ta-ta" , "for so long!" , "Say this before drinking" , "An informal hearty goodbye" , "Expression used when leaving" .)