Chap leaving aggregate stone (5)
I believe the answer is:
agate
'stone' is the definition.
(agate is a type of stone)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for agate that I've seen before include "Precious stone" , "Decorative stone" , "Semi-precious quartz" , "Old drama critic" , "Quartz with bands of colour, used in jewellery" .)