What to do with this Exeggutor?

I wouldn't - although that's a good defensive move set, the IV is low and Exeggutor won't sit high in gyms. I'd wait for a better move set and IV. You should look at the Silph Road Nest Atlas for any Exeggcute nests near you and visit them.

I'd power it up to 2100 at least... it's worth adding to lower CP gyms and you might stay in there longer than you think.

What are the chances of you getting a better one? you'll need to catch/hatch a good exeggcute, and then get the same moveset... it could very well cost you hundreds of candy before getting a 80+C/P exeggutor. Bringing that one up to a usable level will cost you way less.

I personnaly would power it up, especially if you don't have a lot of strong defenders. You should be able to gather more candies that you need to keep him maxed out and evolve other exeggute. If you happen to get a better C/P latter, you'll have two great defenders. That can't be a bad thing.

hell, I powered up my 67%ZH/P as defensive mon. He is my 2nd best, defenders are hard to find (1st being my maxed out vaporeon, 3rd my lapras that I can't power up since I lack candy... and then less relevant mons like slowbro, average vaps, poliwrath). He is one of the only good non-water defender, and for me that's enough of a reason to max him out.

edit: at level 30, he'll be about 2380, vs 2440 for a 82% and 2500 for a 100%.

My Confusion / Psychic Exeggutor is one of my best defenders, and I keep him nearly maxed out (around 2600 CP now). It took my 6 evolutions to get that moveset. I don't see Eggs much in gyms anymore since the buff, but I think they are solid defenders. You just need to get him to high enough CP depending on your gym situation. So, if you have the dust and candies to get him to like 2200-2500, I say go for it. If you don't have it yet, then collect the candies in the meantime until you can do it in one shot... who knows you might get a better IV one later.

Exeggutor was nerfed a little with the CP update, but its max CP is still pretty good.
https://pokemongo.gamepress.gg/cpcalc#/
You can use the CP calculator to see how high you can get its CP at your current level (1.5 levels higher than your current player level). Compare that with your current defenders to better decide if it is worth the investment. Depending on IV distribution, 69% should get close to 2400 cp at level 30.

Power it up. If you get a better one power that one up too. Your Exeggutor has a good move set and the IVs are good enough.

For now it seems great to power it up, but consider will you want to keep powering it up every time you level? If so then go for it. I think this comes down to personal preference mostly. I Ignored IVs early on and now am locked into powering up my mediocre IV Exeggutors each level.

I personally wouldnt come close to considering anyway below 82%IV

And would wait.

But obviously its up to you. IVs are not everything, but im assuming you would be much happier with one at 85%+

And if that's the case you don't wonna waste your dust/candy

I wouldn't