Stop working for tycoon (5)
I believe the answer is:
baron
'tycoon' is the definition.
('baron' can be a synonym of 'tycoon')
'stop working' is the wordplay.
'stop' becomes 'bar' (I've seen this before**).
'working' becomes 'on'.
'bar'+'on'='BARON'
'for' acts as a link.
(Other definitions for baron that I've seen before include "Powerful financier" , "British peer of the lowest rank" , "powerful man owning lots of dailies?" , "Lowest rank of British nobility" , "An English lord or a magnate" .)