Metal tip of spear pierces fish (5)
I believe the answer is:
brass
'metal' is the definition.
(brass is a kind of metal)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for brass that I've seen before include "cash" , "section of orchestra" , "Alloy; money" , "Metal - cheek" , "Alloy (associated with muck)" .)