"You're So Vain" singer Carly (5)
I believe the answer is:
simon
'you're so vain singer carly' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for simon that I've seen before include "Sir -- Rattle, conductor" , "Harris and Coveney" , "- and Garfunkel" , "- Templar, The Saint" , "Peter (NT)" .)