Ladies and Gents south of Waterloo vacant (5)
I believe the answer is:
women
'ladies' is the definition.
(I know this)
'gents south of waterloo vacant' is the wordplay.
'gents' becomes 'men' (gent can mean a man).
'south of' says to put letters next to each other.
'vacant' means to remove the middle letters (a vacant or emptied out form of the word).
'waterloo' with its middle removed is 'wo'.
'men' put after 'wo' is 'WOMEN'.
'and' acts as a link.
(Other definitions for women that I've seen before include "Ladies" , "Adult human females" , "half of our race" .)