What's coming up in television film? (5)
I believe the answer is:
sheet
'film?' is the definition.
(film is a kind of sheet)
'what's coming up in television' is the wordplay.
'what' becomes 'eh' (sound used to ask 'what?' or 'pardon?').
'coming up' shows that the letters should be reversed in order (in a down clue, letters go up).
'in' means one lot of letters goes inside another.
'television' becomes 'set' (television set).
'eh' backwards is 'he'.
'he' inserted within 'set' is 'SHEET'.
(Other definitions for sheet that I've seen before include "Piece of paper; nautical rope" , "Mattress cover" , "leaf" , "Page of postage stamps" , "It usually gets blanket coverage" .)