Type of spear often seen in depictions of Poseidon (7)

I believe the answer is:

trident

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'type of spear' is the definition.
(I know that trident is a type of lance)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for trident that I've seen before include "spear carried at sea" , "Nuclear weapon" , "Red tint? (anagram)" , "3-pronged spear" , "not pike" .)

I've seen this clue in The Times.

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