Crossword Genius

I left without keys and one ring for a hobbit (5)

Ross

I believe the answer is:

bilbo

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

'a hobbit' is the definition.
(I've seen this before)

'i left without keys and one ring' is the wordplay.
I cannot really understand how this works, but
'i' is present in the answer.
'left' could be 'l' (common abbreviation) and 'l' is found in the answer.
'ring' could be 'o' and 'o' is found within the answer.
This explanation may well be incorrect...

'for' is the link.

Can you help me to learn more?

(Other definitions for bilbo that I've seen before include "___ Baggins, a leading hobbit" , "The Hobbit hero" , "Rapier - I blob (anag)" , "sword" , "Frodo's uncle (LOTR)" .)

I've seen this clue in the Evening Standard.
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