I have a full grid but not sure how these clues "work"
There is an extra letter in the wordplay in each clue
17a Jerk contracted back muscles for striking effects - ans is ECLATS
26a Display about current account returning capital - ans is ACCRA - is it "air" for show +c(about) + ca (current account)??
23a American cockchafer poked round mounds - ans is DORBU - dorbuG is the US cockchafer beetle but "poked round mounds"???