ladanum
lamaism
leftism
legroom
lehayim
libitum
lithium
locoism
lustrum
I'm sure there are many in the dictionary, but the first one that pops to mind is "manual".
A seven letter word that starts with D and ends with T: decrypt
A seven (7) letter word that starts with M and ends with O: memento
Duchess is a seven letter word.
descentdecideddiamonddiscarddiscorddividedelevateerasuregaininggrowingglowinghellishlateralliterallogicalmodicumoreganoreentertangenttrident
anxiety
andiron
malaria
cardiac
stomata
Cabomba
Alveoli.
rotator