On Mars a peculiar blue? (7)

I believe the answer is:

oarsman

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'blue?' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.

'on mars a peculiar' is the wordplay.
'peculiar' indicates an anagram.
'on'+'mars'+'a'='onmarsa'
'onmarsa' anagrammed gives 'OARSMAN'.

Can you help me to learn more?

(Other definitions for oarsman that I've seen before include "One in a row" , "galley slave, say" , "He rows" , "It's bordered by Libya and France" , "Male rower" .)

I've seen this clue in The Sun.

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