Rejection of novel by unknown ultimately unfair, journalist complained (8)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

Y (=unknown, in algebra) + AMME (EMMA=novel, by Jane Austen; “rejection of” indicates reversal) + <unfai> R (“ultimately” means last letter only) + ED. (=journalist, i.e. editor); to yammer is to whine, wail, hence “complain”