Core Treant Protector?

Treant Protector can be a SEMI-carry, his base damage and strength gain are high, but he doesn't scale at all beyond this. Don't get farming items ( Maelstrom is about your only option here, but you don't want the game going late by AFK farming if he's your main carry).

I once ended up playing solo-safe-lane carry in a pub where a 3 stack decided to go aggressive-tri and I needed to carry midgame. Power Treads into Assault Cuirass should be your line here, possibly followed by Daedalus. You want the game over fast.

I'd say his more useful role is utility #3 offlaner, or greedy #4 support. Aghanim's Scepter (ruin enemy jungle and get vision of it as suggested is good) is very useful for team fights. Pipe of Insight, Vladmir's Offering, Blink Dagger etc.