Hard-headed wife interrupts scrap (6)
I believe the answer is:
shrewd
'hard' is the definition.
(similar in meaning)
'headed wife interrupts scrap' is the wordplay.
'headed wife' becomes 'w' (abbreviation. I am not sure about the 'headed' bit.).
'interrupts' indicates putting letters inside.
'scrap' becomes 'shred' (both can mean a small amount of material).
'w' placed into 'shred' is 'SHREWD'.
Can you help me to learn more?
(Other definitions for shrewd that I've seen before include "Astute or crafty" , "Astute in business" , "Sharp-witted" , "Fly" , "Astute, calculating" .)