Expert know-how is a term used to describe the MASTERY of a particular skill or knowledge. It is often associated with having a deep understanding of a subject, and the ability to apply that knowledge in a practical way. Expert know-how is usually acquired through years of experience and study, and is often seen as a sign of expertise in a certain field. The crossword solution for this term is 'MASTERY', which refers to the high level of proficiency and understanding that comes with expert know-how.