Related Clues:

• Reserve to join in combat
• Intervene dramatically, or at a senior level
• Take on (eg for work, in battle)
• Take on - reserve - promise
• Complicated mess
• Snarl-up
• Become interlocked, as gears
• The first fish can do this to fishing line
• Do more than listen
• The French follow strong smell of confusion
• Act as a substitute
• Become involved
• Easily donned, as attire
• Knotted, twisted mass
• The way to get in touch with barman to give her a ring perhaps