[Grammar] teenagers, who nowadays lacks authority

[mateuszek123]

"Contemporary society is demanding when it comes to a role model for teenagers, who nowadays lacks authority from which they can take an example"
I don`t know how to correct the bolded part of the sentence, there is a grammar mistake, but I do not really know how to change it correctly. thanks in advance

 

[emsr2d2]

The third word in bold is a verb. It needs to agree with the noun to which it refers. What is that noun?