ITV user's excited about Oscar's sort of humour (8)
I believe the answer is:
vitreous
'sort of humour' is the definition.
(vitreous humour is part of the eye)
'itv user's excited about oscar's' is the wordplay.
'excited' is an anagram indicator.
'about' means one lot of letters goes inside another.
'oscar' becomes 'O' (phonetic alphabet: alpha, bravo, charlie etc.).
'itv'+'user'='itvuser'
'itvuser' anagrammed gives 'vitreus'.
'vitreus' enclosing 'o' is 'VITREOUS'.
(Other definitions for vitreous that I've seen before include "Made of glass" , "Having glass-like finish or texture" , "Glassy" , "Resembling glass - over suit (anag)" , "How glaze appears" .)