Sour beer found in Eastern Mediterranean (10)
I believe the answer is:
embittered
'sour' is the definition.
(thesaurus)
'beer found in eastern mediterranean' is the wordplay.
'beer' becomes 'bitter' (bitter is a type of beer).
'found in' is an insertion indicator.
'eastern' becomes 'e'.
'mediterranean' becomes 'med' (I've seen this in other clues).
'e'+'med'='emed'
'bitter' inserted into 'emed' is 'EMBITTERED'.
(Other definitions for embittered that I've seen before include "Made resentful" , "Made more sour" .)