Nancy's one place to sleep that has no beams? (5)
I believe the answer is:
Here is my best explanation:
'that has no beams?' is the definition.
(without beams of light)
'nancy's one place to sleep' is the wordplay.
'nancy's one' becomes 'un' ('one' in French, eg in the city of Nancy).
'place to sleep' becomes 'lit' ('bed' in French**).
(Other definitions for unlit that I've seen before include "Perhaps invisible", "not exactly bright", "Shady", "Left in the dark", "Not yet fired up", "Lacking illumination", "Shadowy", "With no lighting", "not provided with a lamp?" and "such as dark alley?".)