Suddenly attack ruffian hugging tree (4,3)
I believe the answer is:
lash out
'suddenly attack' is the definition.
(to lash out is to suddenly attack)
'ruffian hugging tree' is the wordplay.
'ruffian' becomes 'lout' (I've seen this before).
'hugging' means one lot of letters goes inside another.
'tree' becomes 'ash' (ash tree is a kind of tree).
'lout' placed around 'ash' is 'LASH OUT'.
(Other definitions for lash out that I've seen before include "fight vigorously" , "React aggressively" , "Spend extravagantly" , "React violently" , "Wildly attack" .)