Bananas found in messy lair -- see creature (9)
I believe the answer is:
armadillo
'creature' is the definition.
(armadillo is a kind of creature)
'bananas found in messy lair see' is the wordplay.
'bananas' becomes 'mad' (slang for insane).
'found in' means one lot of letters goes inside another.
'messy' indicates anagramming the letters.
'see' becomes 'lo' (archaic exclamation meaning 'look!').
'lair' with letters rearranged gives 'aril'.
'mad' going into 'aril' is 'armadil'.
'armadil'+'lo'='ARMADILLO'
(Other definitions for armadillo that I've seen before include "Nocturnal creature" , "Insect eater" , "Scaly burrowing animal" , "Burrowing mammal with a covering of bony plates" , "Nocturnal animal" .)