Stone made entrance (5)
I believe the answer is:
agate
'stone' is the definition.
(I've seen this before)
'made entrance' is the wordplay.
'made' becomes 'a' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'entrance' becomes 'gate' (I've seen this before).
'a'+'gate'='AGATE'
Can you help me to learn more?
(Other definitions for agate that I've seen before include "Quartz variety" , "Variety of chalcedony" , "Old drama critic" , "marble" , "Semi-precious quartz" .)