One tuning in to hear Leinster getting demolished! (8)
I believe the answer is:
listener
'one tuning in to hear' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'leinster getting demolished' is the wordplay.
'getting demolished' indicates anagramming the letters.
'leinster' is an anagram of 'LISTENER'.
Can you help me to learn more?
(Other definitions for listener that I've seen before include "Tough crossword" , "One attending" , "One pays attention in order to hear" , "Difficult Times Saturday crossword" , "One lending an ear" .)