The visitors ran up 282 for six after losing the toss, Clarke making 59 and Liam Patterson-White contributing a belligerent 46 not out.
There were two wickets each Jack Brooks and Tom Abell as a depleted Somerset seam attack stuck to their task and kept a grip on the scoring rate.
By the time bad light ended play for the day 7.2 overs early, Patterson-White and Tom Moores (26 not out) had added 74 precious runs for the seventh wicket.
With Craig Overton away on England duty and Lewis Gregory nursing a back injury, Somerset were deprived of two key seam bowlers.
It showed as Notts edged the morning session in heavily overcast conditions, despite the early loss of Ben Slater, caught at backward point by Tom Lammonby, looking to cut Brooks.
Ben Duckett and Sam Northeast took the total to 44 before Duckett, on 24, skied a pull shot off Brooks and the catch was comfortably taken by Roelof van der Merwe at cover.
Northeast enjoys batting at Taunton and moved confidently to 33 by lunch, which was taken at 88 for two, with Clarke on 21.
The afternoon session saw Northeast depart with the total advanced to 97, lbw looking to drive a Josh Davey delivery into the on-side.
Clarke brought up the hundred with a top-edged six over third-man off Brooks before moving to a solid half-century off 97 balls, with 5 fours.
The former Worcestershire batsman was looking in good touch and it was a surprise when he got a thin bottom edge, attempting to pull Abell and wicketkeeper Steve Davies took the catch.
Lyndon James and Steven Mullaney exercised caution in adding 32 before tea, which was taken at 172 for four.
The gloomy conditions and cold wind continued into the final session. Notts had added 22 runs when James edged a defensive shot off Abell through to Davies and fell for 30.
The pattern of batsmen getting a start and not going onto a big score continued when skipper Mullaney, on 42, aimed to whip a straight ball from Marchant de Lange through the leg side and departed lbw.
At 208 for six, with the new ball less than five overs away, Somerset sensed a big chance. But Patterson-White had other ideas, improving Notts position the over before it was taken by striking three crisp fours off de Lange.
The left-hander bludgeoned six more boundaries in facing just 38 balls, doing much to swing the balance of play Notts' way.
The second new ball did little for the Somerset seamers, who had no complaints when play was called off for the day at around 6pm.