Light-headed drunken sot - simply gone! (4)
I believe the answer is:
lost
'simply gone' is the definition.
'lost' can be an answer for 'gone' (synonyms). I am unsure of the 'simply' bit.
'light-headed drunken sot' is the wordplay.
'light-headed' becomes 'l' (this could be a standard abbreviation of which I'm unaware).
'drunken' indicates anagramming the letters.
'sot' anagrammed gives 'ost'.
'l'+'ost'='LOST'
Can you help me to learn more?
(Other definitions for lost that I've seen before include "Mislaid or astray" , "Unable to find the way forward" , "Unable to be found" , "See 8" , "TV show" .)