Quite sour cocktail, like a Swimming Pool? (9)
I believe the answer is:
turquoise
'like a swimming pool?' is the definition.
(a swimming pool might be turquoise)
'quite sour cocktail' is the wordplay.
'cocktail' indicates an anagram.
'quite'+'sour'='quitesour'
'quitesour' anagrammed gives 'TURQUOISE'.
(Other definitions for turquoise that I've seen before include "Blue-green" , "Birthstone for December" , "Shade of blue - gemstone" , "Precious stone" , "Bluey-green" .)