THEME:   people who may be considered "swingers"   
GOOD ONES:     Important word for {theme}   SWING   
Body part that smells   NOSE [surprised this clue passed the "breakfast test"]   
Not at all well-done   RARE   
Bulletin board material   CORK [I thought info.]   
Feathery layer   HEN   
Forest floor flora   FERN [how's that for onomatopoeia!  Reminds me of Walter de la Mare's "The Listeners"]      
BTW:   Like cough syrup   ORAL [not really --- it's taken orally; the medicine itself is not oral, meaning 
related to the mouth]      
PETRI is off-the-wall hard for a Wednesday (and for me  

 ); but it didn't have to be.  It took five minutes, less, to avoid the name:   
   Change PETRI to 
DOUBT; SWING to 
SESTA; and AFT to 
ODS [OD's means overdoses]
   Thus ANTI becomes 
ONUS, FERN becomes 
DEBT, and TRIG becomes 
SRTA [senorita title address]      
RATING:    
 
 
Three grins = Loved it; Two grins = Enjoyed it; One grin = A bit bland for my taste; One teardrop = Not much fun