Sealed the deal; shut down the business (6)
I believe the answer is:
closed
'sealed' is the definition.
(associated in meaning)
'deal shut down the business' is the wordplay.
I cannot quite understand how this works, but
'shut' could be 'close' (synonyms) and 'close' is found within the answer.
'down' could be 'd' and 'd' is present in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'the' acts as a link.
Can you help me to learn more?
(Other definitions for closed that I've seen before include "Terminated" , "Blocked off" , "clinched the sale" , "Not longer open" , "Held in private" .)