Sailor healthier after whiskey (6)
I believe the answer is:
whaler
'sailor' is the definition.
(I know that whaler is a type of Jack)
'healthier after whiskey' is the wordplay.
'healthier' becomes 'haler' ('hale' can be similar in meaning to 'healthy').
'after' says to put letters next to each other.
'whiskey' becomes 'W' (phonetic alphabet: alpha, bravo, charlie etc.).
'haler' put after 'w' is 'WHALER'.
(Other definitions for whaler that I've seen before include "Ship hunting large mammals" , "Mammal-hunting boat" , "Ship armed with harpoons" , "Occupation of Melville's Captain Ahab" , "one may go to work at sea" .)