Hence, misaal-e-yaar would mean an exemplary lover, a lover that would be sung praises of.
The line, 'misaal-e-yaar ki main, misaalon ko palat doon' would mean, I will change the exemplars of an exemplary lover, i.e. I shall be such a good lover that no one else would be called the best, most exemplary lover, other than me.
By the way, Misaal-e-yaar is a relatively unheard term. Visaal-e-yaar, meeting with the beloved, is one of the more popular terms, which sounds almost the same except for one letter.