A respectful term for one's own older sister or someone else's older sister. Used in formal or polite contexts, often in traditional settings.
My older sister always looks out for me (honorific).
Your older sister is very beautiful (honorific).
Compound of 姉 (ane, 'older sister') and 上 (ue, 'above'), literally 'honored older sister'. The suffix 上 is an honorific used for respected family members.