Animal disturbed gorilla, not good, eating bananas (9)
I believe the answer is:
'animal' is the definition.
(armadillo is a kind of animal)
'disturbed gorilla not good eating bananas' is the wordplay.
'disturbed' is an anagram indicator (the order of letters is disturbed).
'not' is a deletion indicator.
'good' becomes 'g' (abbreviation).
'eating' means one lot of letters goes inside another.
'bananas' becomes 'mad' (slang for insane).
'gorilla' with 'g' taken away is 'orilla'.
'orilla' with letters rearranged gives 'arillo'.
'arillo' enclosing 'mad' is 'ARMADILLO'.
(Other definitions for armadillo that I've seen before include "Bony-plated insectivore" , "Insect-eating mammal" , "Insectivorous mammal" , "Mammal covered with bony plates" , "Horny-plated creature" .)