Crossword puzzle clue "grid footwear"

Grid footwear

Puzzle theme which appears nine more times in the grid

Annual solving competition held in Brooklyn, briefly ... and a hint to nine squares in this grid

How the answer to this clue goes in the grid

What you can find in the grid after completing this puzzle, looking up, down, left, right and diagonally, word search-style

Seasonal card represented by this puzzle's grid

Longhorn's grid rival

Okay, and a hint at what to add to this grid and where