Lacking regard for the feelings of others (13)
I believe the answer is:
inconsiderate
'lacking regard for the feelings of others' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for inconsiderate that I've seen before include "Lacking thought for others" , "Lacking regard for the feelings of others" , "Careless" , "uncharitable" , "showing no regard for others" .)