Farah running with a black eye doesn't finish? Nonsense! (9)
I believe the answer is:
moonshine
'nonsense' is the definition.
(I've seen this in another clue)
'farah running with a black eye doesn't finish?' is the wordplay.
'farah' becomes 'mo' (Sir Mo Farah, British Olympian).
'running' becomes 'on' (eg when a machine is running it is on).
'with' means one lot of letters go next to another.
'a black eye' becomes 'shiner' (synonyms).
'doesn't finish?' means to remove the last letter.
'shiner' with its last letter taken off is 'shine'.
'mo'+'on'+'shine'='MOONSHINE'
(Other definitions for moonshine that I've seen before include "still makes it" , "Nonsensical talk - illicit liquor" , "rot" , "dodgy booze" , "hard stuff" .)