Mother of masterly little ones? (4)

I believe the answer is:

mama

I'm a little stuck... Click here to teach me more about this clue!

'mother' is the definition.
(mama informally means mother)

I cannot understand how the rest of the clue works.

(Other definitions for mama that I've seen before include "Mother" , "Mature woman" , "Dam" , "Mummy" , "Mum" .)

I've seen this clue in the Evening Standard.

Want a hint initially instead of a full solution? Install my app