buckles
Kicks begins with "k" and the 4th letter is "k".
Some six letter words with second letter U and fourth letter K are:bucketbucklebunkercuckooduckedduckiehunkerhuskedjunkedjunkerjunketluckedlurkedmuckedmusketmuskoxpuckerpunkedquakesruckussuckersulkedsunkentuckedturkey
vodka
skirts
Hockey.
Kicks Kooky
walkedwalkerweakenweakerweaklyweeklywickedwinkedworkedworker
kumala or kumata
One such word is hooks.
U (fourth, third, fourth, third, etc).
KeepingKnelledKeelingKillersKingpinKnowing
barrackberserkcassockcowlickcarsickearmarkgoshawkhammockhassockhemlockoutlookpadlockransackrecheckrestockseasick