Since then, has bustled about to hurry up (6)
I believe the answer is:
hasten
'to hurry up' is the definition.
(I've seen this in another clue)
'since then has bustled' is the wordplay.
I cannot quite understand how this works, but
'since' could be 'as' (I've seen this in other clues) and 'as' is present in the answer.
an anagram of 'then' is 'hten' which is located in the left over letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'about' acts as a link.
Can you help me to learn more?
(Other definitions for hasten that I've seen before include "Make faster" , "Speed up" , "Hurry along" , "dash" , "Act or move fast" .)