Smart chap holding hat raised is mark of a soft-spoken character (7)
I believe the answer is:
cedilla
'mark of a soft-spoken character' is the definition.
'cedilla' can be an answer for 'mark' (cedilla is a kind of mark). I am not sure about the 'of a soft-spoken character' bit.
'smart chap holding hat raised' is the wordplay.
'smart chap' becomes 'alec' (as in the phrase 'smart Alec').
'holding' indicates putting letters inside.
'hat' becomes 'lid' (lid can informally mean a hat).
'raised' is a reversal indicator (going up in a down clue).
'alec' enclosing 'lid' is 'allidec'.
'allidec' backwards is 'CEDILLA'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for cedilla that I've seen before include "I called (anag.)" , "foreign accent" , "Mark suggesting a 'c' should be pronounced an 's'" , "Sign to soften C" , "Diacritical mark" .)