I'm old and accept changing is difficult (11)
I believe the answer is:
complicated
'difficult' is the definition.
(thesaurus)
'i'm old and accept changing' is the wordplay.
'and' says to put letters next to each other.
'changing' indicates anagramming the letters.
'im'+'old'+'accept'='imoldaccept'
'imoldaccept' with letters rearranged gives 'COMPLICATED'.
'is' is the link.
(Other definitions for complicated that I've seen before include "confused" , "Not simple" , "Tricky" , "consisting of many interconnecting parts" , "Intricate, difficult" .)