Crossword Genius

One turn may be free of charge (7)

Ross

I believe the answer is:

neutron

I'm a little stuck... Click here to teach me more about this clue!

'free of charge' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.

'one turn may be' is the wordplay.
'may be' indicates an anagram.
'one'+'turn'='oneturn'
'oneturn' anagrammed gives 'NEUTRON'.

Can you help me to learn more?

(Other definitions for neutron that I've seen before include "Uncharged subatomic particle" , "Uncharged particle in a nucleus" , "Turn one (anag) - kind of bomb" , "On tuner (anag.)" , "Elementary particle with zero charge" .)

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