The term 'deep down' can be described by four crossword solutions: INWARDLY (8 letters), INSIDE (6 letters), NETHER (6 letters) and atheart (7 letters). INWARDLY refers to something that is done or felt internally, while INSIDE refers to the inner part of something. NETHER means lower or beneath, and atheart is an adverb meaning in one's heart or soul. All of these words describe something that is hidden or located deep within a person or thing.