Possible Clues:

• A quarter of the year gone yellow with age
• Rather old concern kingship engendered
• Getting on, afraid to follow naughty porn sign
• Reason clock won't wind up yellow and grey (like 19)?
• Getting on well: valiant all round?
• Stylised drama? Well, Coward's getting past it
• Old bird out of bounds?
• Getting on to police — pinching conkers!
• Past one's prime
• Over the 27-Across