Jam and cream going on last bits of traditional scone (6)
I believe the answer is:
pickle
'jam' is the definition.
(synonyms)
'cream going on last bits of traditional scone' is the wordplay.
'cream' becomes 'pick' (both can mean the best of something).
'going on' means one lot of letters go next to another.
'last bits of' indicates one should take the final letters.
The final letters of 'traditional scone' are 'le'.
'pick'+'le'='PICKLE'
'and' is the link.
(Other definitions for pickle that I've seen before include "tricky spot" , "Marinate" , "imp" , "Steep - predicament" , "Immerse (object) in acid" .)