Eccentric people -- cleaner reacts badly (10)
I believe the answer is:
characters
'eccentric people' is the definition.
'characters' can be an answer for 'people' (character is a kind of person). I'm not sure about the 'eccentric' bit.
'cleaner reacts badly' is the wordplay.
'cleaner' becomes 'char' (charwoman is a type of cleaner).
'badly' indicates anagramming the letters (letters in the wrong order).
'reacts' with letters rearranged gives 'acters'.
'char'+'acters'='CHARACTERS'
Can you help me to learn more?
(Other definitions for characters that I've seen before include "Persons in a play/book" , "Eccentrics" , "Signs" , "Roles; letters" , "eccentric people?" .)