John's back in good time? Not quite (6)
I believe the answer is:
nearly
'not quite' is the definition.
(thesaurus)
'john's back in good time?' is the wordplay.
'back' indicates one should take the final letters.
'in good time?' becomes 'early' (being early is arriving in good time).
The last letter of 'john' is 'n'.
'n'+'early'='NEARLY'
(Other definitions for nearly that I've seen before include "Almost, well-nigh" , "Give out a bright light" , "parsimoniously" , "Not entirely" , "Almost, not quite" .)