A child in a blue and white striped shirt crosses his arms and smiles while standing on red carpeted stairs.
A child is smiling as he watches a clown.
The child may be smiling at something else, not a clown.
A child smiles not only when he watches a clown but also on so many other occasions.
A child crossing his arms and smiling  while standing on red carpeted stairs doesn't imply that the child is watching a clown.