```python
def path_clean(path: str) -> str:
    """
    Clean a path by removing every segment of two dots by dropping it together with the segment standing before it,
    and return what remains joined by slashes. Two dots with nothing before them are dropped alone.
    """
    # Split the path by slashes to work with segments
    segments = path.split('/')
    
    # Filter out segments that are either two dots or are empty
    cleaned_segments = [segment for segment in segments if segment != '..' and segment != '']
    
    # Join the cleaned segments back together with slashes
    cleaned_path = '/'.join(cleaned_segments)
    
    return cleaned_path
```