Yeoman of the Guard live performance amid unbridled jeers (9)
I believe the answer is:
beefeater
'yeoman of the guard' is the definition.
(synonyms)
'live performance amid unbridled jeers' is the wordplay.
I cannot quite see how this works, but
'live' could be 'be' (synonyms) and 'be' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for beefeater that I've seen before include "Royal servant" , "no vegetarian?" , "Yeoman of the Guard; carnivore" , "One might guard" , "Tower of London guard" .)