Which figure of speech is used in this text?
Zoe's Boutique claims to have "something for everyone," but it is generally understood that their target market is women of a certain age.

 - euphemism
 - paradox
The text uses a euphemism, a polite or indirect expression that is used to de-emphasize an unpleasant topic.
Of a certain age is an indirect and generally more polite way of referring to older people.