Memory defect mother raised upset first-class nurse once (7)
I believe the answer is:
amnesia
'memory defect' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'mother raised upset first-class nurse once' is the wordplay.
'mother' becomes 'ma' (ma can mean mother).
'raised' is a reversal indicator (going up in a down clue).
'upset' says the letters should be written in reverse.
'first class' becomes 'ai' (A1 - top quality).
'nurse once' becomes 'SEN' (abbreviation for state-enrolled nurse).
'ma' back-to-front is 'am'.
'ai'+'sen'='aisen'
'aisen' backwards is 'nesia'.
'am'+'nesia'='AMNESIA'
Can you help me to learn more?
(Other definitions for amnesia that I've seen before include "Partial or total loss of memory" , "Seaman I found in state of memory loss" , "Disorder" , "Main sea (anag.)" , "Defect in memory" .)