“LASTLY” is a valid word. — 9 points Scrabble

lastthe temporal end; the concluding time
staycontinuing or remaining in a place or state
talla garment size for a tall person
salta compound formed by replacing hydrogen in an acid by a metal (or a radical that acts like a metal)
allya friendly nation
laysa narrative song with a recurrent refrain
slaykill intentionally and with premeditation
alls
latsthe basic unit of money in Latvia
slata thin strip (wood or metal)
sall
altsangular distance above the horizon (especially of a celestial object)

allquantifier; used with either mass or count nouns to indicate the whole number or amount of or every one of a class
saythe chance to speak
laya narrative song with a recurrent refrain
satthe seventh and last day of the week; observed as the Sabbath by Jews and some Christians
las
sal
slymarked by skill in deception
alsthickening of tissue in the motor tracts of the lateral columns and anterior horns of the spinal cord; results in progressive muscle atrophy that starts in the limbs
styan infection of the sebaceous gland of the eyelid
lata broad flat muscle on either side of the back
altangular distance above the horizon (especially of a celestial object)
tas
ays

ata highly unstable radioactive element (the heaviest of the halogen series); a decay product of uranium and thorium
asa very poisonous metallic element that has three allotropic forms; arsenic and arsenic compounds are used as herbicides and insecticides and various alloys; found in arsenopyrite and orpiment and realgar
ya
laa white soft metallic element that tarnishes readily; occurs in rare earth minerals and is usually classified as a rare earth
ala silvery ductile metallic element found primarily in bauxite
ay
taa hard grey lustrous metallic element that is highly resistant to corrosion; occurs in niobite and fergusonite and tantalite

LASTLY