Mother's holding a doctor's snakes (6)
I believe the answer is:
mambas
'snakes' is the definition.
(mamba is a kind of snake)
'mother's holding a doctor's' is the wordplay.
'mother's' becomes 'mas' (ma is a kind of mother).
'holding' indicates putting letters inside.
'doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus**).
'a'+'mb'='amb'
'mas' going around 'amb' is 'MAMBAS'.
(Other definitions for mambas that I've seen before include "these snakes bite dangerously" , "Arboreal snakes" .)