She has nothing over Ruby (5)
I believe the answer is:
freda
'she' is the definition.
(I've seen this before)
'nothing over ruby' is the wordplay.
'nothing' becomes 'fa'.
'over' indicates putting letters inside.
'ruby' becomes 'red' ('red' can be a synonym of 'ruby').
'fa' placed around 'red' is 'FREDA'.
'has' is the link.
(Other definitions for freda that I've seen before include "woman" , "Female name; fared (anag.)" , "Girl's name" , "Girl" .)