Some mistake lambasting pack leader (5)
I believe the answer is:
akela
'leader' is the definition.
(I have seen 'Leader of pack' mean 'akela' so perhaps 'leader' could also mean 'akela')
'some mistake lambasting pack' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'AKELA' is hidden within 'mistake lambasting pack'.
(Other definitions for akela that I've seen before include "Cubs leader" , "Adult Cub Scout leader" , "Cub Scout pack leader" , "Cub Scouts adult leader" , "Leader of pack of Cub Scouts - she-wolf in "The Jungle Book"" .)