Tone in empty bar: call from landlord to stop drinking outside? (6)
I believe the answer is:
timbre
'tone' is the definition.
(I know that tone can be written as timbre)
'empty bar call from landlord to stop drinking outside?' is the wordplay.
'empty' means to remove the middle letters.
'call from landlord to stop drinking' becomes 'time' (as in a publican calling time).
'outside?' indicates putting letters inside.
'bar' with its centre removed is 'br'.
'br' placed within 'time' is 'TIMBRE'.
'in' is the link.
(Other definitions for timbre that I've seen before include "Distinctive sound quality" , "Characteristic quality of sound" , "Sound's character" , "Quality of sound of the voice" , "Quality of voice, sounds wooden" .)