Usually, I'm alone in a bar - about 1,000 beers I've drunk (9)
I believe the answer is:
semibreve
'usually i'm alone in a bar' is the definition.
I can't tell whether this definition defines the answer.
'1000 beers i've drunk' is the wordplay.
'1000' becomes 'M' (roman numeral).
'drunk' is an anagram indicator.
'm'+'beers'+'ive'='mbeersive'
'mbeersive' with letters rearranged gives 'SEMIBREVE'.
'about' is the link.
(Other definitions for semibreve that I've seen before include "2 minims/4 crotchets" , "Note equal to two minims" , "Note equivalent to four crotchets" .)