knack, knock, kayak, kapok, kiosk
Special bonus: klunk
5 letter words beginning with g ending with L:grillgrowl
They're simply words with six letters beginning in e and ending in you.
Five letter words starting with H and ending in H are:hatchhaughfeathheighheuchheughhitchhoochhunchhutchhumphhorahhotchharsh, heath.
Partnership
Ten letter words beginning with A and ending with C:AchromaticAllergenicAlphabeticAltruisticAnalyticalAnestheticAntitheticApologeticApoplecticArithmeticAstigmaticAstronomic
colic
civic
facetfaintfaultfightfirstflintflirtfloatfleetfrontfrostfruit
Beseech, bewitch
undercutunionistuppercut
HARM
Suez.