Founder of some business in Knightsbridge (4)
I believe the answer is:
sink
'founder' is the definition.
(sinking is a kind of foundering)
'some business in knightsbridge' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'SINK' is hidden in the letters of 'business in knightsbridge'.
'of' acts as a link.
(Other definitions for sink that I've seen before include "Basin for washing up etc" , "Succeed in putting" , "Drop beneath the surface" , "Plumbing fixture" , "(Cause to) become submerged" .)