Look at what's sitting in the middle of Astroturf: the answer is hiding in plain sight, and "is too much for" is the nudge that Astroturf holds it inside itself (as TROT is a short form of Trotskyist). The definition is left-winger, a political radical of the Trotskyist sort. So it's a hidden word, with the wordplay and the definition sitting at either end of the clue.