Investigate or Study Something to Find Out More
Puzzle 11 of Ghost Hunting Hard Pack
Question is: Investigate or Study Something to Find Out More
and the answer is: RESEARCH
Word Meaning:
RESEARCH — (uncountable, countable in some dialects) Diligent inquiry or examination to seek or revise facts, principles, theories, applications, etc. (that are currently available, or that are familiar to one's self).
Definitions from Wiktionary.