Kristian Dennis scored his 12th goal of the season to give struggling Chesterfield a 1-0 victory over promotion-chasing Exeter at the Proact Stadium.Dennis scored from a corner early in the second half and although Chesterfield had defender Scott Wiseman dismissed in the final minute, they deservedly won at home for the first time under manager Jack Lester.Both teams cancelled each other out for most of the first half although Exeter striker Liam McAlinden flashed a shot across the face of goal in the 38th minute before Dennis had a shot charged down a minute later.But no-one got to Dennis in the 50th minute when a corner flashed across the goal and he drove a left-footed shot past Christy Pym from eight yards.McAlinden just failed to turn in a low cross from Dean Moxey in the 68th minute and in the 86th minute his 25-yard shot bounced back off the bar.But although Wiseman was sent off for a second yellow in the 90th minute, Chesterfield held on for a vital win.