Possible Clues:

• Byword for keenness is leading performer in wet conditions
• The keen stuff ?
• Leaves eaten as cooked greens
• 40A/34D topping
• Bother with problem that's coming up, showing standard of keenness
• If it's so hot, a doctor has to come back for it
• Damaging allegation about famous actor - hot stuff!
• Yellow condiment
• Fairy like 13
• Being so hot, got to be hard for the cockney