Sardine can (3)
I believe the answer is:
tin
'sardine can' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tin that I've seen before include "1 down, symbol Sn" , "Ready" , "Silvery-white metallic element" , "Kind of metal often used as food container" , "Silvery-white metal used in cans" .)