Whole time alto was performing (5)
I believe the answer is:
total
'whole' is the definition.
(similar in meaning)
'time alto was performing' is the wordplay.
I cannot really see how this works, but
'time' could be 't' (abbreviation) and 't' is found within the answer.
an anagram of 'alto' is 'otal' which is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for total that I've seen before include "Ruin" , "Unqualified" , "It might be grand" , "The whole number" , "Count" .)