In The Thick Of Meaning

(idiomatic) In the middle of (something difficult).

Example: 2011 January 15, Phil McNulty, “Tottenham 0 - 0 Man Utd”[1], BBC:
  Rooney was fit to return to United's line-up after missing two games with an ankle injury - and he was in the thick of the action right away as he raced on to Dimitar Berbatov's pass only to send a presentable finish wide from an acute angle.