One of those on the phone dealing with what's currently hot (8)
I believe the answer is:
receiver
'one' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'those on the phone dealing with what's currently hot' is the wordplay.
I cannot really understand how this works, but
'on' could be 're' ('on' can be mean 'with reference to') and 're' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
'of' is the link.
Can you help me to learn more?
(Other definitions for receiver that I've seen before include "Person appointed to liquidate or preserve assets" , "Telephone handset" , "One who takes stolen goods" , "One is appointed to liquidate or preserve assets" , "Fence; bankruptcy official" .)