It's sweet with celery and gin in a salad (9)
I believe the answer is:
glycerine
'it's sweet' is the definition.
(I know that glycerine is sweet)
'celery and gin in a salad' is the wordplay.
'and' means one lot of letters go next to another.
'in a salad' is an anagram indicator (salad can mean a mixture).
'celery'+'gin'='celerygin'
'celerygin' with letters rearranged gives 'GLYCERINE'.
'with' acts as a link.
(Other definitions for glycerine that I've seen before include "What's in bangers" , "Viscous material used in antifreeze" , "Syrupy chemical liquid" , "Alcohol" , "Sweet stuff" .)