Star, losing heart, takes terrible chance (8)
I believe the answer is:
asterisk
'star' is the definition.
(I know that star can be written as asterisk)
'losing heart takes terrible chance' is the wordplay.
'losing heart' suggests removing the centre.
'terrible' indicates an anagram.
'chance' becomes 'risk' (synonyms).
'takes' with its centre taken out is 'taes'.
'taes' is an anagram of 'aste'.
'aste'+'risk'='ASTERISK'
(Other definitions for asterisk that I've seen before include "Star-shaped symbol as reference mark." , "Star of typography" , "Sarkiest (Anag)" , "Star for the printer" , "Star-like symbol as reference mark" .)