Bright in initially crowded bar (6)
I believe the answer is:
clever
'bright' is the definition.
(bright can mean clever or intelligent)
'initially crowded bar' is the wordplay.
'initially' suggests taking the first letters.
'bar' becomes 'lever' (lever is a kind of bar).
The first letter of 'crowded' is 'c'.
'c'+'lever'='CLEVER'
'in' acts as a link.
(Other definitions for clever that I've seen before include "Deft, able, bright" , "Brainy, smart" , "expert" , "Quick at learning and understanding" , "Mentally or physically skilful" .)