Possible Clues:

• Change agent
• Sounds as if a catalogue will help the cat to get things going
• Tom reading aloud from a register creates reaction
• That's what helps the reaction that pussy gets to an inclination
• With pussy, it seems that a further number of items are needed to get things going
• Agent provocateur thrown out of Italy, headless
• Chemical influencing change
• Reaction enhancer
• Feline leaning, by the sound of it, to fasten things up, perhaps
• Agent taking one pound from sum received by actors