Heavyweight in enclosure initially explaining sound of phone (8)
I believe the answer is:
ringtone
'sound of phone' is the definition.
'ringtone' can be an answer for 'sound' (I have seen 'Mobile sound ' mean 'ringtone' so perhaps 'sound' could also mean 'ringtone'). I am not sure about the 'of phone' bit.
'heavyweight in enclosure initially explaining' is the wordplay.
'heavyweight' becomes 'ton' (a ton weighs a lot).
'in' means one lot of letters goes inside another.
'enclosure' becomes 'ring' ().
'initially' suggests taking the first letters.
The initial letter of 'explaining' is 'e'.
'ring'+'e'='ringe'
'ton' put into 'ringe' is 'RINGTONE'.
Can you help me to learn more?
(Other definitions for ringtone that I've seen before include "Sound heard when someone telephones" , "Sound of modern life" , "Sound of a phone on an incoming call" , "Nitrogen (anag.)" , "Sound coming from mobile" .)