Highly acidic character (3)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
phi
'character' is the definition.
(I know that Greek letter is a type of character)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for phi that I've seen before include "Greek letter in previous answer" , "Greek letter; sounds like expression of outrage" , "Greek letter; hip (anag.)" , "exotic character" , "Letter from the Balkans" .)