Race over and see heartless carer (5)
I believe the answer is:
nurse
'carer' is the definition.
(I've seen this before)
'race over and see heartless' is the wordplay.
'race' becomes 'run' (run is a kind of race).
'over' says the letters should be written backwards.
'and' means one lot of letters go next to another.
'heartless' suggests removing the centre.
'see' with its middle removed is 'se'.
'run' in reverse letter order is 'nur'.
'nur'+'se'='NURSE'
(Other definitions for nurse that I've seen before include "Cherish" , "Child minder" , "Take care" , "Carer for the sick; shark" , "drink slowly" .)