There are three; mothers, smother, and thermos.
Using all 7 letters you get rewords
Seven letter words that can be made from those letters are shutter and stretch.
Sinkage is the seven letter word formed using the letters aeigkns.
essayed
Settees
demotic
deleads
wavered
sellout
There are no seven letter words from these letters.
No 7 letter words there. 5 letters is the best you can do: arena or anear
Seven letter words that can be made from those letters are:amnesiapumpkin