Singer has one starting point (5)
I believe the answer is:
basis
'starting point' is the definition.
(I've seen this in another clue)
'singer has one' is the wordplay.
'singer' becomes 'bass' (bass is a kind of singer).
'has' indicates putting letters inside.
'one' becomes 'I' (Roman numeral).
'bass' going around 'i' is 'BASIS'.
(Other definitions for basis that I've seen before include "Principal element" , "Principle on which a theory is founded" , "Reason" , "Groundwork, foundation" , "Fundamental part" .)