。
She wears the same kind of clothes as her older sister.
Literal
She [topic-は] older-sister [subject-が] wear [nominalizer-の] [comparison-と] same kind [genitive-の] clothes [object-を] wears.
An embedded-comparison structure: 姉さんが着るの (literally 'the [thing] her sister wears') uses の to nominalize the embedded clause; と同じ marks it as the standard of comparison; 種類の服 ('kind of clothes') is what's compared. Note 着る is reserved for upper-body and full-body garments — different verbs cover lower-body wear (はく), head wear (かぶる), accessories (はめる, かける).