Journalist on drink (8)
I believe the answer is:
reporter
'journalist' is the definition.
(thesaurus)
'on drink' is the wordplay.
'on' becomes 're' ('on' can be mean 'with reference to').
'drink' becomes 'porter' (porter is a kind of drink**).
're'+'porter'='REPORTER'
(Other definitions for reporter that I've seen before include "News journalist" , "media person" , "He gives details" , "News person" , "hacker?" .)