Ray, a French bachelor in bed (7)
I believe the answer is:
sunbeam
'ray' is the definition.
(sunbeam is a kind of ray)
'a french bachelor in bed' is the wordplay.
'a french' becomes 'un' ('a' in French).
'bachelor' becomes 'b' (abbreviation e.g. BA=Bachelor of Arts).
'in' means one lot of letters goes inside another.
'bed' becomes 'seam' ('seam' can be a synonym of 'bed'**).
'un'+'b'='unb'
'unb' put inside 'seam' is 'SUNBEAM'.
(Other definitions for sunbeam that I've seen before include "sheds a bit of light" , "Ray of solar light" , "Bright ray -- bus name (anag)" , "Bright shaft of daylight" , "Ray of natural light" .)