Question: What adjective (single word) means 'having/using a willingness to learn'?

Answer: 
Having a willingness and capacity to learn is **teachability**: 

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> teachable adj.
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> 1. Capable of being taught: teachable skills.
> 2. Able and willing to learn: teachable youngsters.
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> teach′a·bil′i·ty, teach′a·ble·ness n. teach′a·bly adv.
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> American Heritage® Dictionary of the English Language, Fifth Edition.
>  Copyright © 2011 by Houghton Mifflin Harcourt Publishing Company.
>  Published by Houghton Mifflin Harcourt Publishing Company. All rights
>  reserved.
> 
> 
>
"Enthusiastic" is the best word that comes to mind for me. Doing is sort of like learning, so it is similar enough.