Concession securing a TV series? (4)
I believe the answer is:
soap
'tv series?' is the definition.
(soap opera is a type of TV series)
'concession securing a' is the wordplay.
'concession' becomes 'sop' (sop is a kind of concession).
'securing' means one lot of letters goes inside another.
'sop' enclosing 'a' is 'SOAP'.
(Other definitions for soap that I've seen before include "Cleaner - TV programme" , "Serialised drama" , "TV entertainment" , "A cleansing sort of TV serial" , "Bath tablet" .)