Take care, sweetheart (6)
I believe the answer is:
steady
This clue is a double definition.
'take care' is the first definition.
('steady' may be said to tell someone to take care)
'sweetheart' is the second definition.
(both can mean a romantic partner)
(Other definitions for steady that I've seen before include "not easily excited" , "Not wobbling" , "Stayed (anag.)" , "date seen regularly" , "Slow and ... wins the race" .)