Lightning seen on the bed? (5)
I believe the answer is:
sheet
I believe this is a double definition.
'lightning' is the first definition.
(sheet lightning is a kind of lightning)
'seen on the bed?' is the second definition.
(Other definitions for sheet that I've seen before include "Large piece of fabric" , "Single piece of paper" , "newspaper" , "Sail-rope on the bed?" , "Set of unseparated stamps" .)