1a a 3 letter abbrev [not the usual one] for 'born' with a general 3 letter word for 'generation' outside and 'every' extra.
I found the endgame frustrating too, lumen - I got there through trying to expand a couple of the more obscure words (there aren't many options in some of them) and realising there was a common thread. I'd have much preferred a logical process of getting there - and the thematic clues are a very mixed bunch - some minimal, others complex (the 1st, 3rd, 4th and 6th [bar the 3 letter Scots word] are, perhaps, the most straightforward ... and the 2nd as well, but it's a bit skimpy).