Constraint, force (6)
I believe the answer is:
duress
This clue is a double definition.
'constraint' is the first definition.
(I've seen this in another clue)
'force' is the second definition.
(I know that duress is a type of force)
(Other definitions for duress that I've seen before include "Threat of coercion" , "Constraint, coercion" , "Excessive pressure" , "Constraint, Compulsion" , "Illegal coercion" .)