Alternative mum scratched face (5)
I believe the answer is:
other
'alternative' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for other that I've seen before include "One may be significant" , "not like you" , "Very unusual" , "Different (from those mentioned)" , "Distinct" .)