Boast endlessly about ace singer such as Kishore (7)
I believe the answer is:
crooner
'kishore' is the definition.
I can't judge whether this definition defines the answer.
'boast endlessly about ace singer such' is the wordplay.
'boast' becomes 'crow' (crow is a kind of boast).
'endlessly' means to remove the last letter.
'about' is a reversal indicator.
'ace singer such' becomes 'reno' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'reno' in reverse letter order is 'oner'.
'crow' with its final letter removed is 'cro'.
'cro'+'oner'='CROONER'
'as' acts as a link.
Can you help me to learn more?
(Other definitions for crooner that I've seen before include "Crosby or Sinatra?" , "Profession of Bing, Frank or Perry" , "Crosby-type singer" , "Bing Crosby, for example" , "Singer of sentimental songs" .)