Please what is tas-heel

Question
Please what is tas-heel, I'll love to have an audio sample
Answer
Bismillah
Tasheel is a lightening of the reliance on the articulation point of the hamzah so that it is read in between a hamzah and the medd letter which matches the vowel. 
For Hafs 'an 'Aasim there is only one word in the Qur'an read with tas-heel, and that is the second hamzah in the word in surah Fussilaat aayah 44:

in surah FuSSilat , is read with  of the second hamzah between a hamzah and an alif. 

The following link has the correct reading of tas-heel with some explanation in Arabic by his emminence Sheikh Ayman Swayd may Allah preserve him and grant a long life of khair:

https://www.youtube.com/watch?v=T7Mh-UIpRSY