That's awful vague.
A five letter word containing N, K, and U is: plunk
confusion
bureaus
Examples of 5 letter words with the second letter 'u' are:augerburntcurseduncedustyfudgefungifunnyguessguestguilthumanhumorjudgekudzulunchlurchmuralmusicnudgenurseoughtpunchqueenquellquestrummyrumorruralsuavesunnysushitulletumorwurstyuccayummy
quest...
dummy
Graduate.
fungi
ulceruncleuncutundueunderunionuniteunlitunmetuntilunzipupperurbanuntieusageutter
adieu
usher
cubic, tunic