Partner leads the ♠3 and dummy wins the A. Dummy is on the right (can't we fix these diagrams, so the felt is in the middle?).
You play UDCA and Reverse Smith, so lo-high = I like it. Partner's lead of a low card promises an honor (T or higher).
Whatever you play at T1, declarer will play a club to the J and Q, both cards winning.
See poll choices.