import re

def numTidy(number_str):
    # Remove all characters except digits, '-' and '.'
    cleaned_str = re.sub(r'[^\d.-]', '', number_str)
    
    # Ensure only one leading negative sign
    if cleaned_str.count('-') > 1:
        cleaned_str = '-' + cleaned_str.replace('-', '', 1)
    
    # Ensure only one decimal point
    if cleaned_str.count('.') > 1:
        parts = cleaned_str.split('.')
        cleaned_str = parts[0] + '.' + ''.join(parts[1:])
    
    # Remove trailing non-numeric characters
    cleaned_str = re.sub(r'[^0-9]+\Z', '', cleaned_str)
    
    # Validate and format the number
    try:
        number = float(cleaned_str)
        return str(number)  # Return the cleaned number as a string
    except ValueError:
        return ""  # Return an empty string if the cleaned string is not a valid number

# The following line would be used in IDEA to call this function:
# @Python("numTidy", AMOUNT)