Cool bar has core of gilt embedded (7)
I believe the answer is:
inbuilt
'core of gilt embedded' is the definition.
I can't judge whether this defines the answer.
'cool bar' is the wordplay.
'cool' becomes 'in' ('in' can mean fashionable or cool).
'bar' becomes 'built' (I am not sure about this - if you are sure you should believe this answer much more).
'in'+'built'='INBUILT'
'has' is the link.
Can you help me to learn more?
(Other definitions for inbuilt that I've seen before include "Integral" , "Being an original feature" , "essential" , "Native" , "Present from the beginning" .)