Luke-warm (5)
I believe the answer is:
tepid
I believe this clue is a double definition.
'luke' is the first definition.
(thesaurus)
'warm' is the second definition.
(similar in meaning)
(Other definitions for tepid that I've seen before include "Slightly warm" , "Moderately warm" , "Unenthusiastic - cool" , "Warmish" , "Half-hearted" .)