Stones as placed around an entrance (6)
I believe the answer is:
agates
'stones' is the definition.
(I've seen this before)
'placed around an entrance' is the wordplay.
'placed' becomes 'as' (I can't justify this - if you can you should give a lot more credence to this answer).
'around' indicates putting letters inside.
'an entrance' becomes 'gate' (I've seen this before).
'as' going around 'gate' is 'AGATES'.
'as' is the link.
Can you help me to learn more?
(Other definitions for agates that I've seen before include "Multi-coloured quartzes" , "marbles" , "Set aga up for shiny stones" , "Ste aga up for the stones" , "Stones to be found in a stage" .)