if you are able to speak Chinese i think it's better to explain it to you in chinese:
"拥被高卧" :抱着被子睡觉,
“外子还在拥被高卧”:老公在抱着被子睡大觉(外子有老公或外甥的意思,但老公比较常用)
in english,the word means be asleep with quilt covered on sb,
and the sentence tells that the husband is sleeping with a quilt over his body