House containing a splendid building (6)
I believe the answer is:
palace
This clue might be a double definition.
'house' is the first definition.
(palace is a kind of house)
'a splendid building' is the second definition.
'palace' can be an answer for 'building' (I have seen 'Large building' mean 'palace' so perhaps 'building' could also mean 'palace'). I am not certain of the 'a splendid' bit.
'containing' is the link.
Can you help me to learn more?
(Other definitions for palace that I've seen before include "Impressive residence of a ruler" , "See 23" , "Royal mansion" , "eg Buckingham" , "Stately mansion" .)