Sexy Posh perhaps wearing Sporty's or Scary's clothing (6)
I believe the answer is:
steamy
'sexy' is the definition.
(steamy can mean sexy or erotic)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for steamy that I've seen before include "Hot and misty" , "Salacious" , "Full of condensation; erotic (story)" , "Vaporous: lustful" , "Hot and humid - erotic" .)