Exeter moved back to the top of the Premiership table with an unconvincing 14-9 win over battling Bristol at Sandy Park.
The victory took them four points clear of second-placed Saracens, but fierce tackling from the visitors frustrated a Chiefs' side which lacked creation.
It was not until the final 15 minutes that the hosts were able to get their noses in front and get the win.
Ian Madigan kicked three penalties for Bristol to earn his side a deserved bonus point.
Charles Piutau was a late withdrawal for Bristol, having failed to recover from a hamstring problem, but the visitors overcame this setback to have the better of the opening 10 minutes.
Harry Randall's break was the sole highlight of that period but could not capitalise as Tom Pincus was forced into touch.
Bristol continued to dominate and deservedly took the lead when Madigan kicked a simple penalty before the visitors bungled the restart.
This allowed Exeter to have their first attack with neat touches from Cordero and Henry Slade testing the defence but a wayward pass from Ian Whitten prevented them from capitalising.
Chiefs continued their impetus and a strong burst from Matt Kvesic set up a try-scoring opportunity but Ben Moon knocked on when only five metres from the line.
Bristol's defence was admirable but their efforts took its toll when Jack Lam, who failed an HIA assessment, and Lewis Thiede were both forced to leave the field with injuries.
Dan Thomas and John Afoa replaced them before Bears' defence cracked with just 14 seconds of the half remaining when a long pass from Slade sent Cordero over.
Steenson's conversion gave Exeter a 7-3 half-time lead before their opponents brought on Yann Thomas and Harry Thacker for the start of the second half and veteran number eight, George Smith, soon afterwards.
It paid dividends as Bristol won a scrum penalty for Madigan to reduce the arrears to a single point before the hosts replaced their entire front row and scrum half, Jack Maunder.
Randall then hoisted an aimless box kick but Steenson and Phil Dollman collided with each other to concede a penalty, which Madigan knocked over.
Steenson was immediately replaced by Simmonds before Lonsdale finished off a period of tremendous pressure by driving over from close range for the crucial score.