It's the least we can do, little mother! (7)
I believe the answer is:
minimum
'it's the least' is the definition.
(I've seen this in another clue)
'little mother' is the wordplay.
'little' becomes 'mini'.
'mother' becomes 'mum' (informal term for mother).
'mini'+'mum'='MINIMUM'
'we can do' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for minimum that I've seen before include "Least possible quantity" , "Nadir" , "Bottom" , "Lower limit" , "Lowest value" .)