Suited worker crossing river (6)
I believe the answer is:
became
'suited' is the definition.
('become' can be a synonym of 'suit')
'worker crossing river' is the wordplay.
'worker' becomes 'bee' (a worker bee).
'crossing' is an insertion indicator.
'river' becomes 'cam' (river in Cambridge, England).
'bee' placed around 'cam' is 'BECAME'.
(Other definitions for became that I've seen before include "Turned into" , "Changed into" , "Looked good" , "Began to be" , "Got to be" .)