Avoid holding hostage, regularly involving duress
I believe the answer is:
shotgun
'duress' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'avoid holding hostage regularly' is the wordplay.
'avoid' becomes 'shun' (shunning is a kind of avoiding).
'holding' indicates putting letters inside.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternate letters of 'hostage' are 'otg'.
'shun' going around 'otg' is 'SHOTGUN'.
'involving' is the link.
Can you help me to learn more?
(Other definitions for shotgun that I've seen before include "arm" , "piece" , "Noughts (anag) - type of wedding" , "Hunting firearm" , "Smooth-bore weapon" .)