Related Clues:

• Entire
• Couldn't do without
• Couldn't live without
• Required
• Word with organ or sign
• Indispensable
• Should it be required, after 'if'
• Like some organs
• Must-have
• Of utmost importance
• As required, after “if”
• Life-or-death
• Like some signs and statistics
• Of prime importance
• Want ad word