Shake one of those in a bar? (6)
I believe the answer is:
quaver
'shake' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for quaver that I've seen before include ".Speak in a trembling voice" , "Half-crotchet" , "Shake; a short note" , "Tremble - half a crotchet" , "(Of voice) tremble" .)