Change it into simple:
"It is clear that a comprehensive approach is needed to tackle the challenges posed by the Ukraine-Russia war and food crisis."

Complex Sentence: It is clear that a comprehensive approach is needed to tackle the challenges posed by the Ukraine-Russia war and food crisis.
Simple Sentence: Clearly, a comprehensive approach is needed to tackle the challenges posed by the Ukraine-Russia war and food crisis.

Complex to simple:
→ Complex sentence এ 'it is sure' থাকলে Simple sentence এ 'it is sure' এর পরিবর্তে surely হবে।
→ It is sure এর পরের relative pronoun টি বাদ যাবে, এরপরে বাকি sentence টি বসবে।

অন্য দিকে,
→ Complex sentence এ 'it is certain' থাকলে Simple sentence এ 'it is certain' এর পরিবর্তে certainly হবে।
→ Complex sentence এ 'it is suddden' থাকলে Simple sentence এ 'it is sudden' এর পরিবর্তে suddenly হবে।
→ Complex sentence এ 'it is clear' থাকলে Simple sentence এ 'it is clear' এর পরিবর্তে clearly হবে।
→ Complex sentence এ 'it is definite' থাকলে Simple sentence এ 'it is definite' এর পরিবর্তে definitely হবে।

Example:
Complex Sentence: It is clear that the project is progressing well.
Simple Sentence: Clearly, the project is progressing well.

Complex Sentence: It was sudden that he lost his mobile.
Simple Sentence: Suddenly, he lost his mobile.

Complex Sentence: It is definite that the event will take place.
Simple Sentence: Definitely, the event will take place.

Source: A Passage to the English Language, S. M. Zakir Hussain.