The interim government of Bangladesh is working tirelessly to rebuild the nation's trust after years of political turmoil.
The underlined part is a/an -

• The interim government of Bangladesh is working tirelessly to rebuild the nation's trust after years of political turmoil.
- The underlined part is - Non-finite verb and Infinitive.

• A non-finite verb is a verb form that does not show tense.
- Most non-finite verbs found in English are infinitives, participles, and gerunds.

• Infinitive হচ্ছে verb এর base form অথবা to + base form.
• Infintive দুই রকম হতে পারে-
১. To-যুক্ত infinitve এবং
২. To-বিহীন infinitive বা Bare Infinitive.

• আলোচ্য বাক্যে,
- ‘to rebuild’ verb টি কোনো tense নির্দেশ করে না।
- এটা infinitive এবং non-finite verb.

এছাড়াও,
- turmoil (noun) [countable noun, uncountable noun] - গোলযোগ; হাঙ্গামা; গণ্ডগোল।