Nancy's one place to sleep that has no beams? (5)
I believe the answer is:
unlit
'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**).
'un'+'lit'='UNLIT'
(Other definitions for unlit that I've seen before include "such as dark alley?" , "Lacking illumination" , "Not yet burning" , "Dark, gloomy" , "Perhaps invisible" .)