The small “tsu”(っ) is a brief pause. Imagine placing a silent “tsu” that holds a tiny gap in the sound.
When typing, simply double the consonant that follows the pause.
*Romaji is just a guide. Listen to the audio for the real sounds!
きって
kitte (stamp)
きて
kite (Please come.)
かっこ
kakko (parentheses)
かこ
kako (past)
がっき
gakki (instrument)
がき
gaki (little brat))