Break US nettle to disturb (8)
I believe the answer is:
unsettle
'disturb' is the definition.
(I've seen this in another clue)
'break us nettle' is the wordplay.
'break' indicates an anagram.
'us'+'nettle'='usnettle'
'usnettle' anagrammed gives 'UNSETTLE'.
'to' is the link.
(Other definitions for unsettle that I've seen before include "Upset" , "Disrupt" , "Disturb, make anxious" , "Disturb, disconcert" , "Trouble" .)