The visiting Blues found themselves 3-0 down at the break courtesy of goals from Ross McCormack, Rodolph Austin and Matt Smith, before the latter of that trio rounded off the scoring for the home side in the closing stages.
Reflecting on his side's display, Clark described their performance during the first half in particular as "dreadful".
"We were dreadful in the first half in every aspect of the game. We done better things in the second half but we still lost it 1-0. We got we deserved - a heavy defeat," he told the club's official website.
The result means that Clark's men have won just three of their 12 matches this term.