Rare issue put wife at bottom of class (10)
I believe the answer is:
wunderkind
'rare issue' is the definition.
'wunderkind' can be an answer for 'issue' (I have seen 'Extraordinary issue' mean 'wunderkind' so perhaps 'issue' could also mean 'wunderkind'). I am unsure of the 'rare' bit.
'wife at bottom of class' is the wordplay.
'wife' becomes 'w' (abbreviation).
'at bottom of' becomes 'under' (I am not sure about this - if you are sure you should believe this answer much more).
'class' becomes 'kind' (I've seen this in another clue).
'w'+'under'+'kind'='WUNDERKIND'
'put' is the link.
Can you help me to learn more?
(Other definitions for wunderkind that I've seen before include "Extraordinary issue" , "Perhaps Mozart" , "Clever young person" , "One having early success" , "Child prodigy" .)