Tree dweller knocked over weird nifty houses (5)
I believe the answer is:
indri
'tree dweller' is the definition.
(type of lemur)
'knocked over weird nifty houses' is the wordplay.
'knocked over' is a reversal indicator.
'houses' indicates a hidden word (part of the clue houses the answer).
'irdni' can be found hidden inside 'weird nifty'.
'irdni' reversed gives 'INDRI'.
(Other definitions for indri that I've seen before include "Madagascan mammal" , "Short-tailed lemur of Madagascar" , "Large Madagascan lemur" , "Species of lemur" , "native of Madagascar" .)