Possible Clues:

• Sharp-pointed tip on a stem
• Something sharp has king in difficulty
• What's the point, having run into a difficult situation?
• Spike's clerkship quietly removed and reassigned
• Last of lumbar punctures difficulty for spine
• Short spine
• Stinging sensation
• Is this a needle in a large haystack in place that's key?
• Hedgehog spine
• Thorn found right in the vegetable preserve