Betting journalist was rushed (4)
I believe the answer is:
'rushed' is the definition.
('speed' can be a synonym of 'rush')
'betting journalist' is the wordplay.
'betting' becomes 'sp'.
'journalist' becomes 'ed' (short for editor).
'was' is the link.
(Other definitions for sped that I've seen before include "Raced, hurried" , "Travelled quickly" , "Hastened" , "Rushed" , "Moved quickly" .)