Singular dance for an old soldier (6)

I believe the answer is:

lancer

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'soldier' is the definition.
(lancer is a kind of soldier)

I don't understand the remainder of the clue.

(Other definitions for lancer that I've seen before include "Cavalry soldier" , "Spearman (as in dance?)" , "Former cavalryman" .)

I've seen this clue in the Evening Standard.

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