Type of lightning seen on the bed? (5)
I believe the answer is:
sheet
This clue is a double definition.
'type of lightning' is the first definition.
'seen on the bed?' is the second definition.
(Other definitions for sheet that I've seen before include "Large piece of fabric" , "Bedcover" , "Sail-rope on the bed?" , "Item of bed linen like these" , "leaf" .)