Possessions stored up in chalet at seaside (6)
I believe the answer is:
estate
'possessions' is the definition.
(I've seen this before)
'up in chalet at seaside' is the wordplay.
'up' is a reversal indicator (in down clue: letters go upwards).
'in' says the answer is hidden in the clue.
'etatse' is hidden within 'chalet at seaside'.
'etatse' in reverse letter order is 'ESTATE'.
'stored' is the link.
This may not be correct. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for estate that I've seen before include "Piece of land with a lot of houses" , "Rank - housing development - car" , "Nakedness" , "Piece of land with a large house or many small ones" , "The whole of one's worldly goods" .)