Unbalanced as a Highlander with nothing below his waist? (3,2,6)

I believe the answer is:

out of kilter

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'unbalanced' is the definition.
(I've seen this before)

I don't understand the rest of the clue.

(Other definitions for out of kilter that I've seen before include "Unbalanced" , "Not right" , "Skew-whiff" .)

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

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