Promise in a Church as Part of Marriage Ceremony

Puzzle 7 of Women Inventors Hard Pack

Question is: Promise in a Church as Part of Marriage Ceremony

and the answer is: SOLEMNVOW

Word Meaning:

SOLEMN VOW — (Christianity) A deliberate and free promise made to God about a possible and better good, taken by an individual during or after novitiate in a Catholic religious institute.

Definitions from Wiktionary.