The answers to the clues below will have something in common.

1. Retire from boxing
2. Pay reluctantly
3. Start a concert
4. Treat - as in a restaurant
5. Summon courage
6. Mention things that happened long ago
7. Go faster
8. Keep charging things
9. Even things out
10. Pull on a rope to make it taut
11. Goal of religious missionaries
12. Negate financial gain by self-indulgence

Answers:

1. Hang up the gloves
2. Cough up the money
3. Strike up the band
4. Pick up the tab
5. Work up the nerve
6. Bring up the past
7. Pick up the pace 
8. Run up the bill
9. Make up the difference
10. Take up the slack
11. Build up the Kingdom
12. Eat up the profits 

Credit: Bill Ballard (#1-3)