Conceal empty suitcase on Greek island (7)
I believe the answer is:
secrete
'conceal' is the definition.
(I know that secrete is a more specific form of the action conceal)
'empty suitcase on greek island' is the wordplay.
'empty' says to hollow out the word (remove centre letters).
'on' means one lot of letters go next to another.
'greek island' becomes 'crete' (Crete is a Greek island).
'suitcase' with its centre removed is 'se'.
'se'+'crete'='SECRETE'
(Other definitions for secrete that I've seen before include "Form substance for use within body, as liver does bile" , "Cache" , "Hide away" , "Hide - discharge" , "squirrel" .)