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' means one lot of letters goes inside another.
'hat' becomes 'lid' (lid can informally mean a hat).
'raised' says the letters should be written in reverse (going up in a down clue).
'alec' placed around 'lid' is 'allidec'.
'allidec' in reverse letter order 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" .)