Strike yobbo gripping wood (4,3)
I believe the answer is:
lash out
'strike' is the definition.
'yobbo gripping wood' is the wordplay.
'yobbo' becomes 'lout' (I've seen this before).
'gripping' means one lot of letters goes inside another.
'wood' becomes 'ash' (wood from an ash tree).
'lout' enclosing 'ash' is 'LASH OUT'.
(Other definitions for lash out that I've seen before include "Spend extravagantly" , "Become suddenly aggressive" , "Attack, verbally or physically" , "fight vigorously" , "Attack with blows or words - using whip?" .)