Abnormal, like a forgetful elephant? (5)
I believe the answer is:
rogue
'elephant?' is the definition.
(rogue elephant is a kind of elephant)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for rogue that I've seen before include "Rascal or reprobate" , "Dishonest chap; solitary (elephant)" , "Chap in gallery" , "Blackguard" , "Bad guy" .)