expression, noun which may take the genitive case particle 'no'
under the ... administration; within the ... government
Used with a specific administration or government name, often in the pattern 〜政権下で. Functions as a noun-like expression that can modify other nouns with の.
He served as Secretary of State under the Trump administration.
The policy was introduced under the Abe administration.
Compound of 政権 (seiken, 'administration') and 下 (ka, 'under').