Large native flounders nearly new from eastern Med (9)
I believe the answer is:
levantine
'eastern med' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'large native flounders nearly new' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'flounders' is an anagram indicator (I've seen 'floundering' mean this (letters flounder or move around)).
'nearly' means to remove the last letter.
'new' with its final letter removed is 'ne'.
'native' with letters rearranged gives 'evanti'.
'l'+'evanti'+'ne'='LEVANTINE'
'from' acts as a link.
Can you help me to learn more?
(Other definitions for levantine that I've seen before include "Of the east Mediterranean" , "Vehicle in the lead" .)