Related Clues:

• Do a double take
• Behave
• Make a move
• Slam on the brakes, e.g.
• Do something
• Take countermeasures
• Flinch, say
• Change chemically
• Push back, perhaps
• Don't just sit there
• Jerk one's knee, e.g.
• Don't just stand there
• Strike back
• Answer
• Bounce back