THEME:   Despite the "Twelve Step Puzzle" title I don't know the theme --- I'm sure it's clever, but I lack the patience to figure it out.  
 GOOD ONES:     Zesty start, in London?
   GOOD ONES:     Zesty start, in London?   ZED [Z is first letter of "zesty"]   
When two hands meet?   AT NOON   
Short side?   SLAW ["side" dish of cole "slaw"]   
Household cleaner   RAG [not a product for purchase]   
Gamer's game face   AVATAR [not his expression]   
Peek or bug ending    A-BOO [not the end of snooping]      
BTW:   IRIS-IN is an effect we no longer see in movies --- I suspect it's distracting, except maybe in comedies.      
I'd accept 
quatre and 
sept, but not 
ONZE because the French 4 and 7 are found in words we see and their roots are deciferable; not so of the French 11.      
O.K., I felt bad about the theme so I spent some time on it.  The last word of phrases can precede "STEP."      
RATING:  
 
  
   Three grins = Loved it; Two grins = Enjoyed it; One grin = A bit bland for my taste; One teardrop = Not much fun