Outfit containing superior force (6)
I believe the answer is:
duress
'force' is the definition.
(duress is a kind of force)
'outfit containing superior' is the wordplay.
'outfit' becomes 'dress' (I've seen this in other clues).
'containing' indicates putting letters inside.
'superior' becomes 'u' (I've seen this in other clues).
'dress' placed around 'u' is 'DURESS'.
(Other definitions for duress that I've seen before include "Pressure applied by druses" , "Illegal coercion" , "Use of force or threats to get something" , "Coercion, pressure" , "Coercion, compulsion" .)