“Men, a language is initially spoken” (4)
I believe the answer is:
oral
'spoken' is the definition.
(similar in meaning)
'men a language is initially' is the wordplay.
'men' becomes 'or' (military abbreviation for Other Ranks).
'is initially' indicates taking the first letters.
The first letter of 'language' is 'l'.
'or'+'a'+'l'='ORAL'
(Other definitions for oral that I've seen before include "Via the mouth" , "By word of mouth, like some exams" , "Relating to speech" , "By word of mouth (4)" , "By word of mouth, say exam" .)