Understanding secured, we hear (4)
I believe the answer is:
tact
'understanding' is the definition.
(thesaurus)
'secured we hear' is the wordplay.
'secured' becomes 'tacked' (tacking is a kind of securing).
'we hear' indicates a 'sounds like' (homophone) clue.
'tacked' is a homophone of 'TACT'.
(Other definitions for tact that I've seen before include "Fine perception" , "Consideration and sensitivity" , "Skill in dealing with people" , "Sensitivity (in dealing with others)" , "Consideration in dealing with others" .)