Understand that this clingy behavior is completely normal. Learning to become independent is a scary process and can't be achieved overnight. Every child goes through separation anxiety(fear of separation from one or both parents)at some point in their lives. Your child is no different. Don't expect too much. Let him grow at his own pace.
Give your toddler reasons to be secure. Cuddle him, love him and give him lots of encouragement.
Prepare your toddler in advance when going places with groups of people where you think he will be nervous or when he is typically clingy. If you will be leaving your child in someone else's care, familiarize him with the person and their home before doing so.
Give him some room. Don't always rush to his side when you think he might need you. Encourage him to play with others and step back a little. Remain available if he does need you, but not hovering over him watching his every move.
Don't let your toddler see you stressed out or worried about him when leaving him in another's care. Your anxiety will pass onto him and it will be harder for him to accept. Leave confidently and on a positive note, making sure to tell him all the fun things you will do together when you return.
Say goodbye to your toddler when leaving him in the care of someone else, even if he puts up a fuss. Give him lots of hugs and kisses and let him know you will be back very soon. Sneaking away is not helpful if you have a clingy toddler. He never knows when you might disappear and this could actually make the clinging worse. Don't worry, he'll calm down shortly as he gets distracted with other things and will get used to it after its done enough times.
Remember this clingy phase will pass. Your toddler will not grow up to be a thirty- year-old hanging on your leg in the kitchen. Enjoy that your child needs you at this time in his life. As frustrating as it can be right now, some day you will wish for it back.