Possible Clues:

• Plant with prickly flower heads
• Grant requires particular envelope to return prickly plant
• Prickly-leafed plant
• Tenor receiving artistic support's a prickly one
• The artist needs to have it at last for a nap
• Make fun of half a century and have a nap with it
• Plant with prickly flower head
• Spiny-flowered plant
• Rib apprentice for getting prickly plant
• Elates (anag.)