Reprobate son taking daughter's place during meal (6)
I believe the answer is:
sinner
'reprobate' is the definition.
(thesaurus)
'son taking daughter's place during meal' is the wordplay.
I cannot quite see how this works, but
'son' could be 's' and 's' is present in the answer.
'during' could be 'in' (I've seen this in other clues) and 'in' is located in the answer.
This explanation may well be incorrect...
(Other definitions for sinner that I've seen before include "One in error" , "One in breach of moral law" , "Wrong-doer" , "Person straying" , "One who breaches the moral law" .)