At least mother still has her little old skirt (7)
I believe the answer is:
minimum
'at least' is the definition.
'minimum' can be an answer for 'least' (I've seen this before). I am not certain of the 'at' bit.
'mother still has her little old skirt' is the wordplay.
I cannot really see how this works, but
'mother' could be 'mum' (informal term for mother) and 'mum' is present in the answer.
'her' could be 'min' and 'min' is present in the answer.
A single letter 'i' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for minimum that I've seen before include "Smallest possible quantity" , "Lowest point" , "Least recorded value" , "Least possible quantity" , "Nadir" .)