I think what you are hearing is a reverse string effect blended with a cello. So the reverse string or guitar comes in right before the slow attack of the cello. There are many ways to get a reversed string effect. Some plugins do it for you, or you could do it the old fashion way (play it then reverse it)
Not sure what the reverse instrument is, but it sounds like a stringed instrument.
I was trying to come up sound without using blending, but this may be answer.
Like solarsound said, I would use a sustained note of the cello, bounce that and reverse it, maybe time-stretch it a bit and add some fading-in. If you listen carefully it’s not the same note/sound as the cello melody coming in exactly after the reversed sound.
Yep, reverse sound is used on top of the cello . (the reverse it could be any orchestra element, as long as it has reverb to it and then it`s reversed) . Hope it helps.