अन्वयः

चिन्तयमानस्य as he was thinking, तस्य his, पूर्वम् formerly, अनेन by such, शब्दवेधिना Capable of hitting the target by following the sound, अज्ञानात् without knowledge, यत् which, कृतम् has been committed, दुष्कृतम् sinful, कर्म act, प्रत्यभात् flashed back.

M N Dutt

As he was thinking, the sinful act which he had through ignorance formerly committed by means of the shaft which hits by sounds, rose up in his recollection,

Summary

While he was thus reflecting on a sinful act he had inadvertently comitted long ago, the act of discharging an arrow that could hit its target following the sound, flashed in his mind.

पदच्छेदः

तस्य	तद् (६.१)
चिन्तयमानस्य	चिन्तयमान (√चिन्तय् + शानच्, ६.१)
प्रत्यभात्	प्रत्यभात् (√प्रति-भा लङ् प्र.पु. एक.)
कर्म	कर्मन् (१.१)
दुष्कृतम्	दुष्कृत (१.१)
यद्	यद् (१.१)
अनेन	इदम् (३.१)
कृतं	कृत (√कृ + क्त, १.१)
पूर्वम्	पूर्वम् (अव्ययः)
अज्ञानाच्	अज्ञान (५.१)
छब्दवेधिना	शब्द–वेधिन् (३.१)

छन्दः

अनुष्टुप् [८]

छन्दोविश्लेषणम्

१	२	३	४	५	६	७	८
त	स्य	चि	न्त	य	मा	न	स्य
प्र	त्य	भा	त्क	र्म	दु	ष्कृ	तम्
य	द	ने	न	कृ	तं	पू	र्व
म	ज्ञा	ना	च्छ	ब्द	वे	धि	ना