Positioned one King I see like 21? (7)

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

Positioned one King, I see, like 21? SAT (=positioned, placed) + I (=one) + R (=king, i.e. rex) + I + C (=see, in textspeak); satiric(al) is “like Swift (=entry at 21)”