Not speaking about in time (6)
I believe the answer is:
minute
'time' is the definition.
(I've seen this before)
'not speaking about in' is the wordplay.
'not speaking' becomes 'mute' (I've seen this before).
'about' is an insertion indicator.
'mute' enclosing 'in' is 'MINUTE'.
(Other definitions for minute that I've seen before include "Extremely small" , "Tiny like time unit (6)" , "Sixty seconds" , "Little - bit of time" , "Small; short time" .)