Duress isn’t involved but stability (10)
I believe the answer is:
sturdiness
'stability' is the definition.
(thesaurus)
'duress isn't involved' is the wordplay.
'involved' is an anagram indicator (involved can mean confusing or complex).
'duress'+'isnt'='duressisnt'
'duressisnt' is an anagram of 'STURDINESS'.
'but' acts as a link.
(Other definitions for sturdiness that I've seen before include "Strength, solidity" , "Showing muscularity" .)