Queen Victoria's final age? (3)
I believe the answer is:
era
'age?' is the definition.
(both can mean a long time)
'queen victoria's final' is the wordplay.
'queen' becomes 'er' (short for Elizabeth Regina ie Queen Elizabeth).
'final' suggests the final letters.
The last letter of 'victoria' is 'a'.
'er'+'a'='ERA'
(Other definitions for era that I've seen before include "Period, age" , "generation, maybe" , "Distinctive period of time" , "Epoch, period" , "Geological age" .)