Essex 180 for 7 (Westley 71, Hutton 3-48) trail Nottinghamshire 293 (Clarke 67, Mullaney 55, James 54, Harmer 4-71) by 113 runs
Brett Hutton returned to Nottinghamshire's LV= Insurance County Championship side to claim three wickets and leave Essex in trouble at the Cloudfm County Ground, Chelmsford.
Fast bowler Hutton had only played once previously this season but ripped up the Essex top order, leaving the hosts 15 for 3, and eventually returned 3 for 48.
Tom Westley led the recovery with a patient 71 as Essex climbed to 180 for 7 in a match which is likely heading towards a draw.
Earlier, Simon Harmer had taken the last four Notts wickets to end his barren run as the visitors were bowled out for 293.
Notts, led by Joe Clarke's 67 and Liam Patterson-White's 31, kept Essex out in the field for an hour and a half as they garnered a second batting point before Harmer wrapped up the tail.
Harmer, who has now taken 38 wickets this season, hadn't taken a scalp for 441 balls, across four matches, but claimed 4 for 16 in 7.1 morning overs.
Clarke hoicked across the line to wide mid-on, Patterson-White - having been dropped twice - was bowled, Luke Fletcher swung to deep midwicket and Hutton was lbw while sweeping. The last of which gave Harmer his 250th Championship wicket.
Nick Browne and Alastair Cook were given half an hour to negotiate before lunch, a period which proved catastrophic for the hosts.
Hutton and Fletcher found good nip with the new ball in the seven overs as Essex's response imploded. Browne nervously prodded at a Hutton ball which threatened to seam back to give Tom Moores a straightforward catch. The bowler-wicketkeeper combo united again two overs later as Cook was drawn into a front-foot drive to an away swinger.
Fletcher joined in the fun to have Michael Pepper caught brilliantly behind to leave Essex mulling over their food on 15 for 3.
Westley repaired the slump by putting on 55 with Paul Walter, 38 with Ryan ten Doeschate and 35 with Adam Wheater, but substantial runs proved difficult to come by on a wearing pitch. The captain, the county's top scorer this season with three centuries along with nine single-figure scores, used his grit to reach a 124-ball half-century.
But other than Westley, Essex's batters struggled to get in. Walter was bowled through the gate by Patterson-White, having stuck around for 84 balls, and ten Doeschate edged Hutton to a wide first slip.
Westley finally departed after almost four hours when Patterson-White bowled him with a turning beauty, before Wheater pulled to deep fine leg next ball.
Harmer and Shane Snater made sure there were no more incidents with an unbroken 37-run stand, with the follow-on target passed.