Meaning of the Sanskrit Word: upasrtanam

  upasṛtānām—of those who have taken complete shelter    SB 5.9.20
  upasṛtānām—the devotees who have taken shelter at Your lotus feet    SB 6.9.43
  upasṛtānām—of the devotees    SB 8.12.47

Can't find any compound Sanskrit words containing upasrtanam.