Practical to separate on reflection, consumed by devastating malice (9)
I believe the answer is:
empirical
'practical' is the definition.
(thesaurus)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for empirical that I've seen before include "established by trial" , "dependent on trial" , "Derived from experience" , "Based on experience or experiment" , "Replica I'm making from observation, not theory" .)