Outhouse of slender construction, excessively short (4-2)
I believe the answer is:
lean-to
'outhouse' is the definition.
(thesaurus)
'slender construction excessively short' is the wordplay.
'slender construction' becomes 'lean' (I can't justify this - if you can you should believe this answer much more).
'excessively' becomes 'too' (to too great a degree).
'short' means to remove the last letter.
'too' with its final letter taken away is 'to'.
'lean'+'to'='LEAN-TO'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for lean-to that I've seen before include "Building put up against another" , "Outbuilding propped against another wall" , "Shed abutting other building" , "Small building resting on side of larger one" , "Building supported by another" .)