Feeling demonstrated by symbol Charlie left out (7)
I believe the answer is:
emotion
'feeling' is the definition.
(I've seen this before)
'symbol charlie left out' is the wordplay.
'symbol' becomes 'emoticon' (I've seen this before).
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'left out' indicates named letters should be taken away.
'emoticon' with 'c' taken away is 'EMOTION'.
'demonstrated by' is the link.
(Other definitions for emotion that I've seen before include "Intuitive feeling" , "Mental feeling" , "Surprise, perhaps" , "eg Anger, fear, joy" , "Anger, perhaps" .)