NCO -- gosh, quietly spoken! (8)
I believe the answer is:
corporal
'nco' is the definition.
(thesaurus)
'gosh quietly spoken' is the wordplay.
'gosh' becomes 'cor' (I've seen this before).
'quietly' becomes 'p' (p for piano and quiet).
'spoken' becomes 'oral' ('oral' can be similar in meaning to 'spoken').
'cor'+'p'+'oral'='CORPORAL'
(Other definitions for corporal that I've seen before include "Like old-fashioned punishment" , "Army rank" , "soldier?" , "NCO next under a sergeant" , "Of the body, say punishment" .)