Family get together with boat for a base at last — but it can crash (5,6)
I believe the answer is:
stock market
'a base at last but it can crash' is the definition.
I can't judge whether this definition defines the answer.
'family get together with boat' is the wordplay.
'family' becomes 'stock'.
'get together' becomes 'met' (I can't explain this - if you can you should give a lot more credence to this answer).
'with' indicates putting letters inside.
'boat' becomes 'ark' (ark is a kind of boat).
'met' placed around 'ark' is 'market'.
'stock'+'market'='STOCK MARKET'
'for' is the link.
Can you help me to learn more?
(Other definitions for stock market that I've seen before include "Place for trading securities" , "Trading place for bulls and bears?" , "Where securities, bonds, etc are traded" .)