Close to booming, boy’s voice reached a PM once (9)
I believe the answer is:
gladstone
'a pm once' is the definition.
(I've seen this before)
'close to booming boy's voice reached' is the wordplay.
I cannot quite understand how this works, but
'close' could be 'on' (I've seen this in other clues) and 'on' is located in the answer.
'boy's' could be 'ads' and 'ads' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for gladstone that I've seen before include "PM no longer" , "So tangled in a small bag like a doctor's" , "Liberal leader" , "Victorian GOM" , "19th-century prime minister" .)