Nice grid.

I loved seeing "Brobdingnagian" as one of the clues.

The posts and the nautical terms had me stumped; the other two groups I solved without too much trouble.

Unfortunately, "game" is not recognised as an answer for one of the remaining groups. I suppose this is technically justified, since "Olympic Games" is never (to the best of my knowledge) used in the singular. Still, I feel that it would have been better if "game" were accepted as a solution in this case. That's a minor (and easily countered) criticism, though.

Overall, I really enjoyed this one. Thanks!