Speed of star with no heart (8)
I believe the answer is:
celerity
'speed' is the definition.
(celerity is a kind of speed)
'star with no heart' is the wordplay.
'star' becomes 'celebrity' (star can mean a famous person).
'with no heart' suggests removing the centre.
'celebrity' with its middle taken out is 'CELERITY'.
'of' acts as a link.
(Other definitions for celerity that I've seen before include "Rapidity, speediness" , "Quickness" , "Haste" , "Swiftness of movement" , "Pace" .)