Lancashire had begun on 126 without loss, but Nathan Wood fell to the last ball of Philip Tufnell's first over without adding to his overnight 67. Fairbrother joined Steve Titchard, who went on to make 79 before he was caught at silly mid-off to give Tufnell his second wicket.
Graham Lloyd got off the mark with a straight six, but made only two more before he was bowled trying to sweep Tufnell and Andrew Flintoff managed only 10 before falling to Angus Fraser.
Fairbrother was then joined by Austin, who hit five fours in his first 25 runs and saw Lancashire to their third batting point, while Fairbrother also picked up the pace.
Mark Lathwell and Piran Holloway achieved their highest scores of the season while holding up Essex at Chelmsford. Lathwell made 87, which included 15 boundaries, while the more cautious Holloway made 90, which spanned 71 overs.
Their third-wicket partnership produced 147, ending when Lathwell edged Danny Law to slip, and provided the basis for Somerset's 246 for 6 between lengthy stoppages for rain.
The visitors, replying to 280, looked poised for a substantial lead as they went beyond 200 with only three wickets down. But after Ashley Cowan had Keith Parsons caught behind, the left-arm spinner Paul Grayson struck in successive overs.
He ended Holloway's resistance by persuading him to pull into the hands of mid-on, and had Mike Burns caught behind. That left Somerset 233 for 6, but Rob Turner and Graham Rose survived the final half-hour as the visitors ended 31 adrift with four wickets left.Reuse content