So this is where we just have to put a word partly associated with the above word.
for eg: car

crash.
So in this way we have to continue.I'll start

Force

Airforce


this is so nice.but i think there are less members to continue this game.

Military

fighter.

This one word game is interesting.I enjoyed playing it.

protector.

I have never played one word game.This game has made an interesting story.I liked it.

defence

These all sub-category comes under defense.Its my favorite game to play.