Song in the middle of alto's range is a catchy number? (6)
I believe the answer is:
lariat
'range is a catchy number?' is the definition.
I can't judge whether this defines the answer.
'song in the middle of alto's' is the wordplay.
'song' becomes 'aria' (aria is a kind of song).
'in the' means one lot of letters goes inside another.
'middle of' indicates the central letters.
The central letters of 'alto' are 'lt'.
'aria' inserted inside 'lt' is 'LARIAT'.
Can you help me to learn more?
(Other definitions for lariat that I've seen before include "Cowboy's rope (of Spanish origin)" , "Line of cowboy" , "Rope to lasso or tether" , "Cowboy's rope, lasso" , "A cowboy's rope with noose" .)