Warehouse holding party in formal dress (6)
I believe the answer is:
godown
'warehouse' is the definition.
(I know that godown is a type of warehouse)
'party in formal dress' is the wordplay.
'party' becomes 'do' (do is a kind of party).
'in' indicates putting letters inside.
'formal dress' becomes 'gown' (I've seen this in another clue).
'do' placed into 'gown' is 'GODOWN'.
'holding' is the link.
(Other definitions for godown that I've seen before include "eastern warehouse" , "Leave university" , "storage facility in India" .)