Changing to it again creates trouble (9)
I believe the answer is:
agitation
'trouble' is the definition.
(thesaurus)
'changing to it again' is the wordplay.
'changing' indicates anagramming the letters.
'to'+'it'+'again'='toitagain'
'toitagain' is an anagram of 'AGITATION'.
'creates' acts as a link.
(Other definitions for agitation that I've seen before include "disquiet" , "restless" , "Commotion" , "Stirring - anxiety" , "State of nervous excitement" .)