Small deed visited by new penalty (8)
I believe the answer is:
sanction
'penalty' is the definition.
(thesaurus)
'small deed visited by new' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'deed' becomes 'action' (I've seen this before**).
'visited by' means one lot of letters goes inside another.
'new' becomes 'n'.
'action' enclosing 'n' is 'anction'.
's'+'anction'='SANCTION'
(Other definitions for sanction that I've seen before include "Give official approval or attach a penalty to" , "Permission or approval as for course of action" , "measure taken against offending country?" , "Go-ahead" , "Penalty for breaking law" .)