King George observing a sign of advancing age (7)
I believe the answer is:
greying
'a sign of advancing age' is the definition.
I can't judge whether this definition defines the answer.
'king george observing' is the wordplay.
'king george' becomes 'gr' (Georgius Rex).
'observing' becomes 'eying' (I've seen this in another clue).
'gr'+'eying'='GREYING'
Can you help me to learn more?
(Other definitions for greying that I've seen before include "(Of hair) showing signs of old age" , "requiring Just for Men?" .)