Mum’s forgoing initial rest? (6)
I believe the answer is:
others
'rest?' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for others that I've seen before include "Not these, alternatives" , "The rest" , "Different from those already mentioned" , "Certainly not us" , "Not the same one already mentioned" .)