en_tn/1ti/05/09.md

be enrolled as a widow

There seems to have been a list, written or not, of widows. The church members met these women's needs for shelter, clothing, and food, and these women were expected to devote their lives to serving the Christian community.

who is not younger than sixty

As Paul will explain in 5:11-16, widows who were younger than 60 years old might get married again. Therefore the Christian community was to care only for widows who were older than 60. (See: rc://en/ta/man/translate/translate-numbers)

a wife of one husband

Possible meanings are 1) she was always faithful to her husband or 2) she had not divorced her husband then married another man.