If you file bankruptcy will you lose your security clearance?

Not necessarily. Every agency is different. Bankruptcy may fall under 'maturity' in the suitability factors for holding a clearance. There may be a concern that you are vulnerable to coercion. If bankrupt the agency may put you on 'aftercare'. This means at certain intervals you will need to prove to the agency via documented evidence that you have your finances under control and that any debt is being reduced.