Lengthy item calling to the lower house: planner upset about that (9)
I believe the answer is:
alpenhorn
'lengthy item calling to the lower' is the definition.
I can't judge whether this defines the answer.
'house planner upset about that' is the wordplay.
'house' becomes 'ho' (abbreviation for house).
'upset' is an anagram indicator.
'about that' indicates putting letters inside.
'planner' is an anagram of 'alpenrn'.
'ho' inserted into 'alpenrn' is 'ALPENHORN'.
Can you help me to learn more?
(Other definitions for alpenhorn that I've seen before include "It's a blast" , "blown up" , "Instrument for communication" , "Swiss wind instrument" , "What plays (over the heads of many)" .)