Projecting part extends upwards within limits (4)

I believe the answer is:

limb

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'projecting part' is the definition.
(I've seen this in another clue)

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for limb that I've seen before include "Arm, leg or wing" , "Branch - arm - leg" , "Branch - member" , "Tentacle" , "Eg, arm, leg" .)

I've seen this clue in The Times.

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