Clarke makes his first start since Christmas as head coach Paul Hull makes a number of changes following the defeat at Bath last weekend.
Regan follows Simon Shaw, Kris Chesney and Hugh Vyvyan into the country's elite ‘200 club’.
The back three is reshuffled with Luke Arscott returning at full-back and brother Tom resuming his usual berth on the right wing. David Lemi is named on the left wing after recovering from injury.
Luke Eves is on England Under-20 duty so Nathan Brew moves in from the wing to partner namesake Neil in the centre.
Robert Sidoli returns to the second row after a lengthy absence as Nathan Budgett rests an Achilles injury, and Alfie To'oala packs down on the blindside.
Hull said: "We can take positives from the first-half performance at Bath. This week has been about refreshing legs and minds, resting people where possible so we're ready to fight another day.
"We've brought some fresh faces into the team which will hopefully give us a bit of energy and we're hoping to keep on improving as we have done the past few weeks.
"Leicester are a very physical team and we have to meet that physical challenge head on and try and get in a position to win the game.”
Bristol Rugby (v Leicester Tigers, Friday 7.45pm):
15 Luke Arscott
14 Tom Arscott
13 Nathan Brew
12 Neil Brew
11 David Lemi
10 Ed Barnes
9 Shaun Perry
1 Alex Clarke
2 Mark Regan
3 Darren Crompton
4 Roy Winters
5 Robert Sidoli
6 Alfie To'oala
7 Joe El Abd (c)
8 Dan Ward-Smith
Replacements
16 Ollie Hayes
17 Wayne Thompson
18 Mark Irish
19 Mariano Sambucetti
20 Redford Pennycook
21 Haydn Thomas
22 Chris Ashwin
