Calf
gaff, guff, gulf, goof, golf
Herself.
Behalfbehoofbeliefcutoffengulf.
ifag
Doff. No idea what it means, but spell check said it was good.
barfbeefbiffbuffbumfchefcoifcuffdeafdoffduffgaffgoofguffgulfhalfhuffjiffleafloafmiff
yourself yourself
Fluff, stuff, buff
flyleaf
off,
firetruck
Some four letter words starting with S and ending with F are:selfserfsurf