Notice a true change to subscription (9)
I believe the answer is:
signature
'subscription' is the definition.
(thesaurus)
'notice a true change' is the wordplay.
'notice' becomes 'sign' (I've seen this before).
'change' is an anagram indicator.
'true' is an anagram of 'ture'.
'sign'+'a'+'ture'='SIGNATURE'
'to' is the link.
(Other definitions for signature that I've seen before include "One's mark" , "distinctive style" , "time indicated by this?" , "Name written by its owner" , "(In music) the sharps or flats that follow the clef and indicate the key" .)