Silent first officer, inept to forget uniform (9)
I believe the answer is:
noiseless
'silent' is the definition.
(thesaurus)
'first officer inept to forget uniform' is the wordplay.
I cannot really understand how this works, but
'first' could be 'noi' (I've seen this in other clues) and 'noi' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for noiseless that I've seen before include "with a silencer?" , "Lionesses (anag) - making no sound" , "Silent, quiet" , "Mum" , "unsound?" .)