It braves a new order but trembles (8)
I believe the answer is:
vibrates
'trembles' is the definition.
The definition and answer can be both to do with motion as well as being verbs in their -s form.
Perhaps they are linked in a way I don't understand?
'it braves a new order' is the wordplay.
'a new order' is an anagram indicator.
'it'+'braves'='itbraves'
'itbraves' anagrammed gives 'VIBRATES'.
'but' is the link.
Can you help me to learn more?
(Other definitions for vibrates that I've seen before include "Resonates, shivers as with sound" , "Moves rapidly to and fro, resonates" .)