Declarer Could Have Done Better
If declarer had cashed the diamond and spade winners before running clubs, then this would have been the position at trick eleven (dummy is about to lead the last club winner):
When dummy leads the seven of clubs, you must discard a heart, declarer throws the ten of spades, and now partner has no defense. This is called a double squeeze; first you are squeezed between hearts and spades; and then partner is squeezed between hearts and diamonds. Neither you nor partner can keep two hearts, so declarer’s Jack of hearts takes the 13th trick.
However, if you had returned a heart at trick two (the point at which you actually returned a spade), this squeeze would not have been possible. The reasons are too complex for this Quiz, but the quick summary is that many squeeze positions have relatively rigid requirements regarding entries; this particular squeeze requires that South have a heart winner in the three-card ending. Deal D006.
To explore alternative lines of play and defense, use this link: https://tinyurl.com/57mns5bv