She told the truth,forshe had nothing to lose. The underlined part is -

• She told the truth, for she had nothing to lose. The underlined part is - Conjunction.
Bangla meaning: সে সত্যটি বলেছিল, কারণ তার হারানোর কিছুই ছিল না।

• For:
English meaning: because; as.
Bangla meaning: কেননা; যেহেতু; কারণ; বলে।

Example:
- She remained silent, for her heart was heavy and her spirits low.
- She told the truth, for she had nothing to lose.

Source: Cambridge Dictionary.