Mercury or Mars, eg (6)

I believe the answer is:

planet

I believe this is a double definition.

'mercury' is the first definition.
(thesaurus)

'mars eg' is the second definition.
(Mars is an example)

(Other definitions for planet that I've seen before include "Eg, Mars or Pluto" , "Eg, Mars, Venus" , "One orbiting star" , "Neptune, for example" , "Eg, a ruby" .)

I've seen this clue in The Times.

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