Heat drug, treating relation (8)
I believe the answer is:
daughter
'relation' is the definition.
(I know that daughter is a type of female offspring)
'heat drug treating' is the wordplay.
'treating' is an anagram indicator (I've seen 'treat' mean this).
'heat'+'drug'='heatdrug'
'heatdrug' with letters rearranged gives 'DAUGHTER'.
(Other definitions for daughter that I've seen before include "Female offspring" , "Female child" , "Girl" , "Relation" , "Family member" .)