Screening show about sleuth Italian's backing (10)
I believe the answer is:
protective
'screening' is the definition.
(thesaurus)
'show about sleuth italian's backing' is the wordplay.
'show' becomes 'prove' (proving is a kind of showing**).
'about' means one lot of letters goes inside another.
'sleuth' becomes 'tec' (short for detective).
'italian' becomes 'it'.
'backing' shows that the letters should be reversed in order.
'it' back-to-front is 'ti'.
'tec'+'ti'='tecti'
'prove' enclosing 'tecti' is 'PROTECTIVE'.
(Other definitions for protective that I've seen before include "Serving to keep safe" , "Shielding" .)