Possible Clues:

• United by a cause
• Joint playing Delilah endlessly
• Joint liability originally accepted by Delia for cooking
• Joined for mutual benefit
• Joint American and Labour leaders misrepresented
• In a league, say
• Joined by, eg, treaty
• Everyone gets to die - that's something like
• Matched, beheaded yet joined in some way
• Word in many union names