When revealed, cast out with a cry of pain (6)
I believe the answer is:
showed
'when revealed' is the definition.
'showed' can be an answer for 'revealed' ('show' can be a synonym of 'reveal'). I am not sure about the 'when' bit.
'cast out with a cry of pain' is the wordplay.
'cast out' becomes 'shed' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'with' indicates putting letters inside.
'a cry of pain' becomes 'ow' (exclamation of pain).
'shed' going around 'ow' is 'SHOWED'.
Can you help me to learn more?
(Other definitions for showed that I've seen before include "Demonstrated or displayed" , "presented" , "Demonstrated or depicted" .)