Down payment is picked up in warehouse (7)
I believe the answer is:
deposit
'down payment' is the definition.
(synonyms)
'is picked up in warehouse' is the wordplay.
'picked up' says the letters should be written backwards.
'in' indicates putting letters inside.
'warehouse' becomes 'depot' (I've seen this before).
'is' in reverse letter order is 'si'.
'si' going into 'depot' is 'DEPOSIT'.
(Other definitions for deposit that I've seen before include "Precipitate" , "Plant" , "Put into, bank account say" , "Sediment or bank lodgment" , "(Money or mineral) put down" .)