In demolishing the dome, very quietly cleaned up (6)
I believe the answer is:
mopped
'cleaned up' is the definition.
'mopped' can be an answer for 'cleaned' (mopping is a kind of cleaning). I am not certain of the 'up' bit.
'in demolishing the dome very quietly' is the wordplay.
I cannot quite understand how this works, but
'quietly' could be 'pp' (musical abbreviation for pianissimo) and 'pp' is found in the answer.
an anagram of 'dome' is 'moed' which is within the remaining letters.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for mopped that I've seen before include "Cleaned or wiped with bundle on end of stick" , "Sponged (up)" , "Swabbed (floor)" .)