/t/ → /k/
Now the plosive alveolar /t/ is followed by a sound that is produced at the back of the mouth, a velar (a /k/or a /g/), so the /t/ is assimilated into a voiceless velar /k/. As you can see, the place of articulation changes, but the manner and the voicing (voiceless) are kept.
/t/ (followed by /k/ or /g/) becomes /k/
Is that clear? ǀ ðæk ˈklɪə ǀ
Put that gun down. ǀ ðæk ˈgʌn ǀ
And here are some natural ocurring examples:
He greets ticket collectors and stationmasters and they return his salute (Julian Barnes, KUSP).
As ideas emerge, get going, start writing and a form will start becoming aparent to you (Michael Rosen, OpenLearn).
And so, Charles’s problem really was about perception of catholicism at court (Mrk Knights, BBC4).
This is the type of work I do with my students in my one-to-one classes. I make them practise these processes with exercises until they improve their comprehension of native speakers and are capable of speaking like that themselves. If you are interested in my classes, you can contact me here.