Fishing spear will be sharp soon, less than 2 seconds! (7)

I believe the answer is:

harpoon

I'm a little stuck... Click here to teach me more about this clue!

'fishing spear' is the definition.
'harpoon' can be an answer for 'spear' (synonyms). I'm not certain of the 'fishing' bit.

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for harpoon that I've seen before include "Whale spear" , "Barbed missile" , "Barbed whale-spear" , "word often used in Moby-Dick" , "Anti-whale weapon" .)

I've seen this clue in the Sydney Morning Herald.

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