Place silicon in a warehouse (7)
I believe the answer is:
deposit
'place' is the definition.
(depositing is a kind of placing)
'silicon in a warehouse' is the wordplay.
'silicon' becomes 'Si' (chemical symbol).
'in' means one lot of letters goes inside another.
'a warehouse' becomes 'depot' (I've seen this before).
'si' put within 'depot' is 'DEPOSIT'.
(Other definitions for deposit that I've seen before include "Sediment or bank lodgment" , "Place" , "Put down - leave behind" , "Part payment in advance to secure goods" , "Put down - initial payment" .)