Musical space travellers (7)

I believe the answer is:

planets

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'space travellers' is the definition.
(planets are objects which travel through space)

I don't understand the rest of the clue.

(Other definitions for planets that I've seen before include "Big bodies" , "Heavenly bodies" , "Celestial bodies" , "Ten laps (anag.)" .)

I've seen this clue in The Globe and Mail.

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