Keep making jam (8)
I believe the answer is:
preserve
I believe this clue is a double definition.
'keep' is the first definition.
(I know that keep is a more specific form of keep up)
'jam' is the second definition.
(jam is a type of preserve)
'making' acts as a link.
(Other definitions for preserve that I've seen before include "Keep safe from spoilage" , "Maintain - jam" , "Maintain in unaltered condition" , "area where game is held" , "defend" .)