Sort of piano, honest! (7)
I believe the answer is:
upright
I believe this is a double definition.
'sort of piano' is the first definition.
(I know that upright is a type of forte-piano)
'honest' is the second definition.
(I've seen this before)
(Other definitions for upright that I've seen before include "not grand" , "with principle" , "Erect - post" , "Standing straight up" , "beyond reproach" .)