Related Clues:
- 'Choppers'
- Vital elements
- Park and drive
- Impression makers
- Machinery parts
- Enforceability, figuratively
- Bit players in a big machine
- Clock innards
- Effectiveness, figuratively
- First, second, reverse, etc
- Force, metaphorically
- They're put in food
- Some working parts
- They aren't major players
- They're engaged