The ornamental design for a trocar for surgicalinstrument, as shown and described.
1. Trocar for surgical instrument
1.1 : Perspective
1.2 : Front
1.3 : Back
1.4 : Left
1.5 : Right
1.6 : Top
1.7 : Bottom
The dashed broken lines in the drawings show portions of the trocar for surgical instrument that form no part of the claimed design; the dash-dotted broken lines in the drawings show boundaries that form no part of the claimed design.