त्वया by you, घोरेण by a horrible, कर्मणा deed, यत् what ever reason, ईदृशम् such, पापम् sin, कृतम् has been committed, (for that reason), सर्वलोकप्रियम् beloved of all worlds, हित्वा renouncing, ममापि for me too, भयम् fear, आपादितम् has overtaken me.

That by doing this horrible deed you have committed a great sin of renouncing Rama, the beloved of all worlds. Therefore I am overtaken by fear.