Throw away unfinished jam (5)
I believe the answer is:
scrap
'throw away' is the definition.
(scrapping is a kind of throwing away)
'unfinished jam' is the wordplay.
'unfinished' means to remove the last letter.
'jam' becomes 'scrape' (both can mean a difficult situation).
'scrape' with its last letter removed is 'SCRAP'.
(Other definitions for scrap that I've seen before include "Drop" , "Fragment or remnant" , "Discard; a bit" , "Tussle over junk metal?" , "A fragment or an informal fight" .)