Three fifths of Spice Girls' focus on sex's inner meaning (6)
I believe the answer is:
spirit
'inner meaning' is the definition.
(spirit can mean meaning or essence)
'three fifths of spice girls' focus on sex's' is the wordplay.
I cannot quite understand how this works, but
'sex' could be 'it' (a common euphemism) and 'it' is present in the answer.
This explanation may well be incorrect...
(Other definitions for spirit that I've seen before include "Strong distilled alcohol" , "Distilled alcoholic drink" , "Ghost or strong drink" , "The sort of drink" , "A shade" .)