Design Wendy Houses (3)
I believe the answer is:
end
'design' is the definition.
(both can mean a purpose or goal)
'wendy houses' is the wordplay.
'houses' says the answer is hidden in the clue (part of the clue houses the answer).
'END' can be found hidden inside 'wendy'.
(Other definitions for end that I've seen before include "Discontinue" , "scrap" , "Extreme" , "Fine" , "Novel by Graham Greene" .)