Drunken unknown following advice (5)
I believe the answer is:
tipsy
'drunken' is the definition.
(thesaurus)
'unknown following advice' is the wordplay.
'unknown' becomes 'y' (algebra).
'following' says to put letters next to each other.
'advice' becomes 'tips' (I've seen this in another clue).
'y' after 'tips' is 'TIPSY'.
(Other definitions for tipsy that I've seen before include "Slightly intoxicated" , "Merry, squiffy" , "Loaded" , "1 over 8" , "A bit drunk" .)