* スカンク (sukanku): This is the most common and straightforward way, a direct loanword from English. It's easily understood.
* You could also describe it more descriptively, for example, by mentioning its features: 臭い動物 (kusai doubutsu - smelly animal) or くさいイタチのような動物 (kusai itachi no yōna dōbutsu - animal like a smelly weasel). This is less precise but works if you need to avoid using a loanword.
Therefore, スカンク (sukanku) is the best and easiest option.