Aussie bowler Fergus O'Neill completed figures of 6-72 as Nottinghamshire battled to continue to set the pace at the top of the County Championship.
Somerset had resumed on 7-295 and were all out for 310, with Archie Vaughan unbeaten on 66 as O'Neill, who had taken both openers on Friday, mowed through the visitors' tail.
The leaders also found batting difficult on their Trent Bridge wicket, their captain Haseeb Hameed removed for a four-ball duck and fellow opener Ben Slater trapped lbw for one.
Nottinghamshire got to 193 all out, with O'Neill contributing 21, and Somerset were 2-73 at the close, with O'Neill still awaiting his first second-innings victim after five overs.
Jordan Cox celebrated his call into the England squad for the second Test against New Zealand by striking a double century before Essex enforced the follow-on to take control of their clash with Leicestershire at Grace Road.
