Manage to protect one once noble edifice (4)
I believe the answer is:
ruin
'noble edifice' is the definition.
'ruin' can be an answer for 'edifice' (ruin is a kind of edifice). I'm unsure of the 'noble' bit.
'manage to protect one' is the wordplay.
'manage' becomes 'run' (both can mean to organise).
'to protect' is an insertion indicator (inserted letters are held or protected).
'one' becomes 'i' (Roman numeral).
'run' enclosing 'i' is 'RUIN'.
'once' is the link.
Can you help me to learn more?
(Other definitions for ruin that I've seen before include "loss of position" , "Irreparably damage" , "State of devastation and destruction" , "Destroy or bankrupt" , "failure" .)