Set up store with nothing in it (5)
I believe the answer is:
found
'set up' is the definition.
(synonyms)
'store with nothing in it' is the wordplay.
'store' becomes 'fund' (synonyms).
'with nothing' becomes 'o' (I am not sure about this - if you are sure you should believe this answer much more).
'in it' means one lot of letters goes inside another.
'fund' enclosing 'o' is 'FOUND'.
Can you help me to learn more?
(Other definitions for found that I've seen before include "To bring into being; cast" , "Establish" , "Launch" , "Start" , "Discovered" .)