Designed a piano in outhouse (6)
I believe the answer is:
shaped
'designed' is the definition.
(thesaurus)
'a piano in outhouse' is the wordplay.
'piano' becomes 'p'.
'in' means one lot of letters goes inside another.
'outhouse' becomes 'shed' (I've seen this before).
'a'+'p'='ap'
'ap' inserted inside 'shed' is 'SHAPED'.
(Other definitions for shaped that I've seen before include "Formed or fashioned" , "Cast or moulded" , "Moulded, wrought" , "modelled" , "Form-filling" .)