caturtha - fourth; ślokera - of the verse; artha - the meaning; ei - this; kaila - gave; sāra - essence; prema - love of Godhead; nāma - the holy name; pracārite - to propagate; ei - this; avatāra - incarnation.

I have given the essential meaning of the fourth verse: this incarnation [Śrī Caitanya Mahāprabhu] descends to propagate the chanting of the holy name and spread love of God.