。
I don't have anything to wear when I go clothes shopping.
Literal
Clothes [object-を] buy [purpose-に] go time [genitive-の] clothes [subject-が] not-exist.
A humorous paradox that's become a well-known internet joke in Japanese. 服を買いに行く ('go to buy clothes') is a standard purpose construction with ~に行く. 時の服 ('the clothes for that occasion') uses の to make the entire preceding clause an attributive modifier of 服. The humor lies in the circular problem: you need presentable clothes to go shopping for clothes. No explicit subject — the speaker's situation is self-evident.