The expression refers to aggressive attacking style where one side leaves multiple pieces attacked, but the opponent cannot take full advantage of it since "they can only take one at a time". Was this said by Tal in an interview or in a book (assuming he was actually the one who said it)? Did he say it originally in Russian? If so - what is the exact Russian expression he used?
I have seen this referred to/attributed to a couple of Tal's games. It is quite likely that he used the saying more than once. If study enough of Tal's games, you'll see that he developed a technique of not retracting his (minor) pieces when they were en prise.
The first reference that I was able to find was in his Havana-1966 game against Bjorn Brinck-Claussen. (Quite likely this position, where he's just moved Ra8!
The saying is also often attributed to his 1968 game against Chikovani, where Tal plays 19 Bxe6 instead of retracting his dark-squared Bishop.
As you can see, in both cases Tal leaves multiple pieces hanging, a psychological strategy that he's used to his advantage.
Hope that helps.