There's fifty odd giants remaining (7)
I believe the answer is:
lasting
'remaining' is the definition.
(thesaurus)
'there's fifty odd giants' is the wordplay.
'there's' means one lot of letters go next to another.
'fifty' becomes 'l' (Roman numeral).
'odd' indicates anagramming the letters.
'giants' with letters rearranged gives 'asting'.
'l' next to 'asting' is 'LASTING'.
(Other definitions for lasting that I've seen before include "Evergreen" , "Permanent" , "Long-lived" , "Enduring" , "there for long while" .)