Fish that’s all but extinct? (4)
I believe the answer is:
sole
'fish' is the definition.
(sole is a kind of fish)
'that's all but extinct?' is the wordplay.
'that' becomes 'sol' (I am not sure about this - if you are sure you should believe this answer much more).
'all but' means to remove the last letter ('all but' can mean 'almost' or 'nearly').
'extinct?' becomes 'ex' (prefix meaning former or onetime).
'ex' with its final letter taken off is 'e'.
'sol'+'e'='SOLE'
Can you help me to learn more?
(Other definitions for sole that I've seen before include "O __ Mio (Neapolitan song)" , "swimmer" , "Fish; part of foot" , "Kind of fish - lose it" , "Flatfish; exclusive" .)