Speechless (3)
'speechless' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for mum that I've seen before include "old lady" , "Palindromic mater" , "Parent - shtoom" , "Silent; parent" , "Silence" .)
'speechless' is the definition.
(I've seen this before)
This is the entire clue.
(Another definition for lost for words that I've seen is " Speechless - like stumped solver?".)