Restore vital aria, one cut at opera (2,8)
I believe the answer is:
la traviata
'opera' is the definition.
(Verdi opera)
'restore vital aria one cut at' is the wordplay.
'restore' is an anagram indicator.
'one' becomes 'I' (Roman numeral).
'cut' indicates named letters should be taken away.
'vital'+'aria'='vitalaria'
'vitalaria' with 'i' removed is 'vtalaria'.
'vtalaria'+'at'='vtalariaat'
'vtalariaat' anagrammed gives 'LA TRAVIATA'.
(Other definitions for la traviata that I've seen before include "Verdi's Dumas opera" , "work" , "Verdi opera" .)