Discretion accepting one's understood (5)
I believe the answer is:
tacit
'understood' is the definition.
(thesaurus)
'discretion accepting one's' is the wordplay.
'discretion' becomes 'tact' (I've seen this before).
'accepting' indicates putting letters inside.
'one' becomes 'i' (Roman numeral).
'tact' placed around 'i' is 'TACIT'.
(Other definitions for tacit that I've seen before include "Understood without being put into words" , "Implied or understood, not put into words" , "without speaking" , "Implied, not spoken" , "Wordless" .)