Hope this helps

Once you get to the save barrel, aka half way through the level, and you re-
renter one of the trees again, look for the red Springin' Spider that goes
way up high to the top of the tree, and use him to get onto the next
platform. Once you're here, use Kiddy to throw Dixie up onto the higher
platform in the tree. Once you get here, use Dixie to take the provided
barrel, and to throw it out the hole above you. If done right, it'll own
Koin, and the DK coin is yours.