Inflammation of the ear (6)
I believe the answer is:
otitis
'inflammation of the ear' is the definition.
(I've seen this in another clue)
'of the ear' is the wordplay.
'of' becomes 'o''.
'the ear' becomes 'titis' (I am not sure about this - if you are sure you should believe this answer much more).
'o'+'titis'='OTITIS'
Can you help me to learn more?
(Other definitions for otitis that I've seen before include "Condition of shell-like" , "pain" , "problem for listener" , "Inflammation of the ear" , "complaint?" .)