Went down and around the South Bank (4)
I believe the answer is:
sank
'went down' is the definition.
('sink' can be a synonym of 'go down')
'and around the south bank' is the wordplay.
'and' becomes 'n' (common abbreviation for 'and').
'around' says the letters should be written backwards.
'the south' becomes 'kas' (I can't justify this - if you can you should give a lot more credence to this answer).
'bank' indicates putting letters inside (outside letters create limits or banks).
'kas' back-to-front is 'sak'.
'n' put within 'sak' is 'SANK'.
Can you help me to learn more?
(Other definitions for sank that I've seen before include "Scuttled" , "Foundered" , "Subsided" , "Fell to the bottom" , "(Of ship) went down" .)