Chap knocking back the French spirit (5)
I believe the answer is:
nigel
'chap' is the definition.
'knocking back the french spirit' is the wordplay.
'knocking back' says the letters should be written backwards.
'the french' becomes 'le' ('the' in French).
'spirit' becomes 'gin' (alcoholic spirit).
'le'+'gin'='legin'
'legin' reversed gives 'NIGEL'.
(Other definitions for nigel that I've seen before include "--- Pargetter, (Archers)" , "-- Gresley, railway engineer" , "-- Kennedy, violinist" , "Chap" , "One knighted by Conan Doyle," .)