Unruly mob, round about end of morning: one of a pair beaten (5,4)
I believe the answer is:
bongo drum
'one of a pair beaten' is the definition.
(bongo drums normally come in pairs)
'unruly mob round about end of morning' is the wordplay.
'unruly' indicates anagramming the letters.
'about' indicates putting letters inside.
'end of' says to take the final letters.
The final letter of 'morning' is 'g'.
'mob'+'round'='mobround'
'mobround' anagrammed gives 'bonodrum'.
'bonodrum' placed around 'g' is 'BONGO DRUM'.
(Another definition for bongo drum that I've seen is " one getting beaten?".)