TTT01 HaPpY Birthday 2021!

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Across
  1. 3. A dog in England does this job (6)
  2. 6. To change the game, take its plug out and go! (8, 4)
  3. 7. Good denim trousers, we hear, emit lots of energy (5)
  4. 9. Celebrate the famous route today! (5-3)
  5. 11. Slight tremor ascending makes you fit? (4, 8)
  6. 13. Young raging Ned creates havoc, but with a little TLC, grows up (9)
  7. 14. In an awkward situation? Sounds like you're going to cry. Never mind, just get some exercise! (10)
  8. 15. Someone's at the door? Must be the good luck we ordered! (8, 2, 4)
  9. 16. Happiness unbounded to the world, especially the equatorial areas (3)
  10. 17. It's a crazy sin to defer a whole decade of decisions and call it a sport! (5, 6)
  11. 18. Seafaring bandits stand taller after a change of heart, opting for love rather than ransacking. (7)
Down
  1. 1. When renting love, it's usually helpful to throw in a U-turn (12)
  2. 2. Subtract the maths, learn and enjoy the remainder (7, 7)
  3. 4. Whether it is! When you take her out, be careful not to hurt her heart. Then ask why~that's hearsay. (6)
  4. 5. The name of the new selfless DIY is confusing (5)
  5. 8. Robot escapes from exploding space rocket because, if this is missing, might as well give it a miss (9)
  6. 10. A: What's my mobile doing with all those bags? B: They'll help it, uh, sound just like a musical instrument! (9)
  7. 12. Contemporary compass; I be?; lift weights on a bench: all in halves guarantees a partially abbreviated long read (3, 2, 5)
  8. 13. A dishevelled man in drag has an important role to play (7)
  9. 15. Overheard in the capital city: "No need to bother now with Ken or a soul!" (6)