Are needs transformed by such a song? (8)
I believe the answer is:
serenade
'such a song?' is the definition.
(serenade is a kind of song)
'are needs transformed' is the wordplay.
'transformed' indicates anagramming the letters.
'are'+'needs'='areneeds'
'areneeds' is an anagram of 'SERENADE'.
'by' acts as a link.
(Other definitions for serenade that I've seen before include "Lover's song" , "Musical piece" , "Sing (for someone on a balcony?)" , "Musical performance, under a lady's window?" , "Evening love song" .)