With a start, he's held up inside store (9)
I believe the answer is:
warehouse
'store' is the definition.
(I know that warehouse is a type of store)
'with a start he's held up inside' is the wordplay.
'with' becomes 'w' (short for with).
'a start' becomes 'arouse' (I can't explain this - if you can you should believe this answer much more).
'held up' is a reversal indicator.
'inside' means one lot of letters goes inside another.
'he' backwards is 'eh'.
'arouse' placed around 'eh' is 'arehouse'.
'w'+'arehouse'='WAREHOUSE'
Can you help me to learn more?
(Other definitions for warehouse that I've seen before include "Depository" , "Storage depot" , "Large retail store" .)