Tear in horrendous fashion (4)
I believe the answer is:
rend
'tear' is the definition.
(I know that rend is a type of tear)
'in horrendous fashion' is the wordplay.
'in' indicates the answer is hidden within the clue.
'REND' can be found hidden inside 'horrendous fashion'.
(Other definitions for rend that I've seen before include "Rip" , "Tear apart, wrench" , "Tear, sunder" , "Tear savagely" , "Tear apart roughly" .)