Quite intricate to fit those words in, especially the >6-letter ones. I had the right idea, I just didn't have the patience at first to try to find the expanding words until your nudges confirmed I was on the right track - so many four and five letter words to test. I stopped at six letters first before I realized I had to go all the way to ENTRAPPED
Snared, the answer to the meta (if you did it right!)
to extract six extra letters. The six letters also gave an alternative of NAPPED, but it was obvious that didn't fit the title and mechanism like APPEND did.