Regional intonation: trace once whiskey imbibed! (5)
I believe the answer is:
twang
'regional intonation' is the definition.
(I've seen this before)
'trace once whiskey imbibed' is the wordplay.
'trace once' becomes 'tang' (I can't justify this - if you can you should believe this answer much more).
'whiskey' becomes 'w' (alpha bravo charlie delta ...).
'imbibed' means one lot of letters goes inside another.
'tang' placed around 'w' is 'TWANG'.
Can you help me to learn more?
(Other definitions for twang that I've seen before include "Harsh sound of plucked string" , "The Sound of Music?" , "Sound of elastic being plucked" , "Sort of sound" , "Nasal accent" .)