Scrap of code will last (6)
I believe the answer is:
morsel
'scrap' is the definition.
(I've seen this in another clue)
'code will last' is the wordplay.
'code' becomes 'Morse' (Morse code).
'last' says to take the final letters.
The final letter of 'will' is 'l'.
'morse'+'l'='MORSEL'
'of' is the link.
(Other definitions for morsel that I've seen before include "Tidbit" , "Part" , "Tiny piece" , "Tasty little piece" , "Bite to eat" .)