Powder used in post-natal clinics (4)
I believe the answer is:
'powder' is the definition.
(talcing is a kind of powdering)
'in post-natal clinics' is the wordplay.
'in' indicates the answer is hidden within the clue.
'TALC' is hidden in the letters of 'post natal clinics'.
'used' acts as a link.
(Other definitions for talc that I've seen before include "I may dust" , "Softest mineral on Mohs hardness scale" , "Mineral used as a toiletry" , "Soft stuff" , "It is used to absorb moisture" .)