Solemn over adolescent getting hooch (6)
I believe the answer is:
poteen
'hooch' is the definition.
(both can mean illicitly produced alcohol)
'solemn over adolescent' is the wordplay.
'solemn' becomes 'po' (as in po-faced).
'over' means one lot of letters go next to another.
'adolescent' becomes 'teen' (I've seen this before).
'po'+'teen'='POTEEN'
'getting' acts as a link.
(Other definitions for poteen that I've seen before include "Illicit Irish drink" , "Illegal drink" , "illicit booze" , "Home made spirit" , "Illicit whiskey (Irish)" .)