Chunk of zinc is originally for cutter (7)
I believe the answer is:
incisor
'cutter' is the definition.
(I've seen this before)
'chunk of zinc is originally' is the wordplay.
'chunk of' says the answer is hidden in the clue.
'INCISOR' is hidden in the letters of 'zinc is originally'.
'for' acts as a link.
(Other definitions for incisor that I've seen before include "Chisel-edged tooth" , "Cutting tooth" , "companion could be Goofy" , "cutter" , "Narrow-edged tooth" .)