Release substance in empty shrine on Greek island (7)
I believe the answer is:
secrete
'release substance' is the definition.
'secrete' can be an answer for 'release' (synonyms). I am not certain of the 'substance' bit.
'empty shrine on greek island' is the wordplay.
'empty' means to remove the middle letters.
'on' says to put letters next to each other.
'greek island' becomes 'crete' (Crete is a Greek island).
'shrine' with its middle removed is 'se'.
'se'+'crete'='SECRETE'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for secrete that I've seen before include "Hide away" , "Hold and send out substance into the body as gland does" , "squirrel" , "Release bodily fluid" , "harbour" .)