Possible Clues:

• Marshland phosphorescence
• Phosphorescent light seen over marshy ground at night
• Person or thing impossible to catch
• It's difficult to catch testament from The Bible by that man with small bunch of hay
• Elusive person
• You¿d be lucky to catch this last testament with nothing going to the thin person (4-1'-3-4)
• Marsh light (4 words)
• Is left behind with nothing at The Strand for Scarlet Pimpernel
• Optical illusion
• While two lips entwined, its flame's short-lived