greengage, you should be seeing a six-letter cardinal, not an ordinal. I'm a bit underwhelmed by the endgame, so I'm not 100% certain my selection is right, but after that I have two three-letter words. The whole lot relates to elements you can see in the initial blank grid.
ONEPO is a proportion of something fuller, if I'm on the right lines, but it's all very tenuous.
Can anyone explain 1, 22, and 29? I have the answers but bits of the wordplay (all of 29's wordplay) elude me.
1 - I don't see how the outside letters of the answer are indicated by 15 formerly (which I assume refers to the answer to 15).
22 - The answer appears to be a jumble of some of the letters of CHUCK WAGON, but there's nothing to indicate the deductions.
29 - Completely baffled by this. I assume it's one of answers that are 12ed. My entry can be 12ed to give two words, neither of which seems to fit the clue.