Fine jet (4)

I believe the answer is:

well

I believe this clue is a double definition.

'fine' is the first definition.
('well' can be similar in meaning to 'fine')

'jet' is the second definition.
(thesaurus)

(Other definitions for well that I've seen before include "boring" , "nicely" , "Spring serving as source of water" , "Source of oil - healthy - goodness!" , "31 [SPRING]" .)

I've seen this clue in The Telegraph.

Want a hint initially instead of a full solution? Install my app