Completely high or low voice good with old number (10)
I believe the answer is:
altogether
'completely' is the definition.
(I know that completely can be written as altogether)
'voice good with old number' is the wordplay.
'voice' becomes 'alto' (alto is a kind of voice).
'good' becomes 'g' (abbreviation).
'with' means one lot of letters go next to another.
'old number' becomes 'ether' (I've seen this in another clue).
'alto'+'g'+'ether'='ALTOGETHER'
'high or low' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for altogether that I've seen before include "totally" , "Completely, on the whole" , "Wholly" , "special to get Hermes trousers" , "Entirely" .)