If there is some unnamed virtue for which ambition is the vice, Thomas More had it, I believe: the desire to be at the center when important things are to be done, because you have the talent for them, and you are willing to serve.
Beware the Allure of the Inner Ring, Crisis Magazine.
I’ve got a tickle in my brain for the right word for that, maybe industry, but I can’t make it show up.
Help?
Head Noises 
aspiration?
Hmmm….maybe, though you can aspire to negative things.
True, but I see ambition as being a positive thing as well as a negative thing.
True, which is part of why my brain itches.
It’s like how you can take pride in something good, and it’s not sinful, or have a holy wrath.
It comes down to the balance, so that implies temperance plays a role, although that’s not definitive.
I was also thinking of the word aspiration. George MacDonald once commented that “Ambition is aspiration turned hell-ward.” Everyone needs aspirations; otherwise, they suffer from “defective love,” which is how Dante defines sloth. Industry is the opposite of sloth; hence, industry requires an ordinate love of work. I imagine that the virtuous opposite of ambition–if not aspiration–must combine a sense of industry, aspiration, and service.
In a sense, charity is an opposite virtue to ambition. But, charity covers a very broad spectrum. The only narrower virtue I can think of is the archaic term “vassalage,” which most famously appears in The Song of Roland. A man with vassalage wants to serve his superiors for the glory of the superiors. I think that Sir Thomas More had this virtue in spades.
A charitable ambition vs a selfish ambition seems like a good division.
Nod.
It’s been said that virtues have been used in the service of evil.
Courage is a virtue but one that has been held by plenty of evil people.
For that matter, unselfish ambition has been used by people in the service of evil.
I think it may just be plain old humility. Or, if you prefer, humble service.
I was going down the path of (disordered) ambition being a combination of pride and avarice, which would go against charity, but charity isn’t what the author is suggesting.
A desire to serve the needs of good is definitely in there.