Annoyance of old king hampered by restraint (7)
I believe the answer is:
chagrin
'annoyance' is the definition.
(I've seen this before)
'old king hampered by restraint' is the wordplay.
'old king' becomes 'GR' (Georgius Rex, Latin for King George).
'hampered by' is an insertion indicator.
'restraint' becomes 'chain' (chain is a kind of restraint).
'gr' put within 'chain' is 'CHAGRIN'.
'of' acts as a link.
(Other definitions for chagrin that I've seen before include "Arching with annoyed disappointment" , "Disappointment, exasperation" , "Annoyance/shame at one's failure" , "Annoy" , "Arching with annoyance and embarrassment" .)