Platform for workers teaching doctor (8,3)
I believe the answer is:
drilling rig
'platform for workers' is the definition.
(oil industry)
'teaching doctor' is the wordplay.
'teaching' becomes 'drilling' (drilling is a kind of teaching).
'doctor' becomes 'rig' (I've seen this in other clues).
'drilling'+'rig'='DRILLING RIG'
(Other definitions for drilling rig that I've seen before include "Oil platform" , "Oil well structure" , "Parade-ground uniform" , "making an impression in Brent?" .)