Texan law enforcer let a greenhorn off (3,4,6)

I believe the answer is:

the lone ranger

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

'texan law enforcer' is the definition.
I know nothing about this answer so I can't judge whether this works.

'let a greenhorn off' is the wordplay.
'off' is an anagram indicator.
'let'+'a'+'greenhorn'='letagreenhorn'
'letagreenhorn' with letters rearranged gives 'THE LONE RANGER'.

Can you help me to learn more?

(Another definition for the lone ranger that I've seen is " role behind the mask".)

I've seen this clue in The Times.

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