Number of women in employment (4)
I believe the answer is:
nine
'number' is the definition.
(nine is a number)
'of women in employment' is the wordplay.
'of' indicates the answer is hidden within the clue.
'NINE' can be found hidden inside 'women in employment'.
(Other definitions for nine that I've seen before include "So many" , "Number IX" , "dancing ladies?" , "Square root of 81" , "A perfect square" .)