Riddled with bullets, was taught a lesson (7)
I believe the answer is:
drilled
'taught a lesson' is the definition.
'drilled' can be an answer for 'taught' (drilling is a kind of teaching). I am not certain of the 'a lesson' bit.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for drilled that I've seen before include "Made a hole with a pointed tool" , "soldiers may be treated thus" , "given military instruction" , "Bored a hole or trained by repetition" .)