Lady with kids least set to ditch car (3)
I believe the answer is:
mum
'lady with kids' is the definition.
(mother)
'least set to ditch car' is the wordplay.
'least' becomes 'minimum' (similar in meaning).
'set to ditch' is a deletion indicator.
'car' becomes 'mini' (Mini Cooper).
'minimum' with 'mini' removed is 'MUM'.
(Other definitions for mum that I've seen before include "Silent; parent" , "Palindromic mater" , "Keep quiet, mother" , "Parent - shtoom" , "Quiet; relative" .)