Ah, well - back to the clue (which,after all, is what this site is about).
Most cryptic clues can be split into a straight definition and a cryptic definition. Finding the split is a good first step.
In this case the clue splits into:
(A) If
(B) When to spill the beans, restraining doubtful statement?
Now, Quixote, you should be able to crack it!