4-Ethylguaiacol, which is the phenolic compound that we associate with the clove aroma in beer, can be produced by Saccharomyces (particularly in wheat strains), but is often a product of Brettanomyces.
Could be an intrusion of native yeast?
"Sometimes when I reflect back on all the beer I drink I feel ashamed. Then I look into the glass and think about the workers in the brewery and all of their hopes and dreams. If I didn't drink this beer, they might be out of work and their dreams would be shattered. Then I say to myself, It is better that I drink this beer and let their dreams come true than be selfish and worry about my liver."