Hi - I have also been trying to find out about Drury Clark's parents (born in circa 1760 and married Flora McDonald). Have you been able to find anything?
Many trees have him as the son of Rev. Benjamin W Clark and Elizabeth Lea however I've also heard that he was the illegitimate son of Thomas Ball (1735-1804) and Susan Lucy Jones (1750-1817). I'm not sure how he ended up with the "Clark" surname if that is the case.