You shouldn't despair researching prior to 1850 it can be done.You will not necessarily get specific information but with a little digging you can come up with what you need. You already have a window to look at for a death record.His youngest child was born in 1846 so he was still alive for the conception of that child.That would put his death between 1845 and 1850 unless he took off for parts unknown and left the family. I would first determine was he living in Tennessee in 1840 and find him in that census.He would have been over 25, married, probably head of household (not necessarily however).If you don't see him, look for other Clarke's or Bostick's and pay close attention and take note of those that DO HAVE a male in the household in the 25 year range. If there are other Clarke's they could be brothers, uncles, or even his father. If you are successful finding him in that census access the land tax records starting with 1849 and start working your way back each year until he no longer shows up. Once you narrow down the span of time then I would look at the Wills and Administration records.Even if your William died without a will there might be an inventory or statement of accounts.You probably won't pinpoint an exact date but you can get close. I probably would also just to be thorough, check and see if you see any Branchs.Branch could be the given name or surname of a grandparent.