Huge building, residence capturing heart of monarch (6)
I believe the answer is:
palace
'huge building' is the 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 sure about the 'huge' bit.
'residence capturing heart of monarch' is the wordplay.
'residence' becomes 'place' (place is a kind of residence).
'capturing' indicates putting letters inside.
'heart of monarch' becomes 'a' (I can't justify this - if you can you should believe this answer much more).
'place' placed around 'a' is 'PALACE'.
Can you help me to learn more?
(Other definitions for palace that I've seen before include "See 16" , "Royal residence" , "Grand building" , "Locality round a monarch's official residence" , "See 23" .)