3 A. Old Olympian swimmer's awfully wise before series - keeping warm (11)
W?I????????
12 A. One that crows get up preposterously with good trick (8) B?G?R???
NB. Several clues contain a misprint in their definition. In clue order, the correct letters give a phrase that explains how solvers should KEEP TRYING [the puzzle's title] to modify some answers before entry. I don't know if either - or both - of these clues are involved in that.