Coaches a blockhead on operations (5)
I believe the answer is:
buses
'coaches' is the definition.
('bus' can be a synonym of 'coach')
'a blockhead on operations' is the wordplay.
'a blockhead' becomes 'b' (head letter of 'block').
'on operations' becomes 'uses' (I can't explain this - if you can you should believe this answer much more).
'b'+'uses'='BUSES'
Can you help me to learn more?
(Other definitions for buses that I've seen before include "Passenger vehicles" , "Public service vehicles" , "Public transport vehicles" .)