Request to render song is delightful (8)
I believe the answer is:
pleasing
'delightful' is the definition.
(similar in meaning)
'request to render song' is the wordplay.
'request' becomes 'plea' (plea is a kind of request).
'to render song' becomes 'sing'.
'plea'+'sing'='PLEASING'
'is' acts as a link.
(Other definitions for pleasing that I've seen before include "agreeable - with 13d" , "Satisfying or appealing" , "making one happy" , "Delightful" , "Gratifying" .)