Beat in blameworthy fashion (3)
I believe the answer is:
lam
'beat' is the definition.
(I know that lam is a more specific form of the action beat)
'in blameworthy fashion' is the wordplay.
'in' indicates a hidden word.
'LAM' is hidden in the letters of 'blameworthy fashion'.
(Other definitions for lam that I've seen before include "Thrash; (US) escape" , "Hit hard, strike" , "Flee hastily" , "Hit hard or repeatedly" , "US criminals commonly escape?" .)