Brother and uncles initially laugh with excitement (8)
I believe the answer is:
brouhaha
'excitement' is the definition.
(thesaurus)
'brother and uncles initially laugh' is the wordplay.
'brother' becomes 'bro' (short for brother).
'and' says to put letters next to each other.
'initially' suggests taking the first letters.
'laugh' becomes 'haha' (ha-ha is a laughing sound).
The initial letter of 'uncles' is 'u'.
'bro'+'u'+'haha'='BROUHAHA'
'with' is the link.
(Other definitions for brouhaha that I've seen before include "Overexcited critical response" , "Noisy and overexcited reaction to something" , "Great fuss" , "Noisy fuss" , "'Confused disturbance, uproar (8)'" .)