Reason why waiter may be annoyed around Spike (5)

I believe the answer is:

piton

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'spike' is the definition.
(I know that piton is a type of spike)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for piton that I've seen before include "Peg used in mountaineering" , "In top (anag.)" , "Peg driven into rock as climbing support" , "Climber's spike" , "Spiked climbing aid" .)

I've seen this clue in The Guardian.

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