Deluded elite marksman, one quietly replaced by another (8)
I believe the answer is:
crackpot
'deluded elite marksman one quietly replaced by another' is the definition.
I can't judge whether this definition defines the answer.
'one quietly replaced by another' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'o' (I've seen this in other clues) and 'o' is found within the answer.
'quietly' could be 'p' (p for piano and quiet) and 'p' is found within the answer.
'another' could be 'r' (I've seen this in other clues) and 'r' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for crackpot that I've seen before include "Fruitcake, screwball" , "crazy type" , "Nut" , "Nutty" , "Ludicrous" .)