Pressure bandage placed across middle of thumb (6)
I believe the answer is:
duress
'pressure' is the definition.
(I've seen this before)
'bandage placed across middle of thumb' is the wordplay.
'bandage' becomes 'dress' (I've seen this in another clue).
'placed across' indicates putting letters inside.
'middle of' means to look at the middle letters.
The middle letter of 'thumb' is 'u'.
'dress' placed around 'u' is 'DURESS'.
(Other definitions for duress that I've seen before include "Coercion, pressure" , "Hardship" , "The use of force or threats to get one's way" , "Illegal coercion" , "Use of force or threats, often vile" .)