Britain's Victoria Pendleton secured the all-important top seeding in the women's sprint competition with an Olympic record in qualifying.
The seedings are decided by a timed 200m sprint from a flying start.
Pendleton delighted London 2012's loudest crowd with a time of 10.724 seconds, 0.081 seconds quicker than Australian rival Anna Meares.
Earlier in Sunday's morning session,
moved into a tie for second place in the multi-event omnium.
Clancy, who was part of the
gold medal-winning team pursuit team,
is two points behind Australia's world champion Glenn O'Shea, with two events remaining in the evening session.
The 2010 world champion will be expected to win the final event of track cycling's answer to the decathlon, the 1km time trial.
That means the result should hinge on the very unpredictable 15km scratch race, which takes place from 17:00 BST.
Pendleton sprints to Olympic track cycling record
That distance is at the top end of Clancy's ideal range, but the real issue for him will the tactical challenge of a first-past-the-post race, with 17 rivals, over 60 laps.
This has traditionally been a relative weakness for the 27-year-old Yorkshireman but he is improving all the time, as he demonstrated in Saturday evening's elimination race, when he stole two points on the line with last-gasp efforts.
Clancy will effectively be riding against O'Shea and the 20-year-old Dane Lasse Norman Hansen, who is tied with the Brit on 19 points. Italy's Elia Viviani is a point behind on 20, with overnight leader Bryan Coquard of France in fifth on 22.
Pendleton was a little outside the world record of 10.643 set by Germany's Miriam Welte in June but broke her own previous Olympic best of 10.963 set in Beijing in 2008.
She recovered from the disappointment of disqualification in the team sprint to
win the gold medal in the keirin on Friday.
In the individual sprint, Pendleton is defending the title she won at Beijing four years ago
in what will be her final Games
Her qualifying effort was a repeat of Jason Kenny's performance in the men's competition on Sunday.
He also set an Olympic record in qualifying, giving him a first-round bye and a relatively straightforward first race to gain access to the last eight.
With an even number of riders in the women's competition, "Queen Vic" does not get a bye, but she is racing the 18th quickest qualifier in this evening's first round from 16:00.
Ekaterina Gnidenko, 19, is a better rider than her qualifying time would suggest, but she is unlikely to deny Pendleton.