Training medic badly (5)
I believe the answer is:
drill
'training' is the definition.
(drill is a kind of training)
'medic badly' is the wordplay.
'medic' becomes 'dr' (doctor).
'badly' becomes 'ill' ('ill' can be adverbial as in 'ill-advised').
'dr'+'ill'='DRILL'
(Other definitions for drill that I've seen before include "Boring machine" , "Bore (a hole); fabric" , "Dental assistant" , "training exercise" , "Square-bashing" .)