adverb, adverb taking the 'to' particle
Adverbial use describing something done or perceived in a clear, unambiguous manner. Often used with verbs like 言う, 見える, わかる.
彼は自分の意見をはっきり言った。
He clearly stated his opinion.
遠くの山がはっきり見える。
The distant mountains are clearly visible.
noun or participle which takes 'suru'
be clear; be definite; become clear
Used with する to describe a state or change of state where something becomes clear, definite, or unambiguous. Often refers to facts, intentions, or situations.
彼の態度ではっきりした。
His attitude made it clear.
方針がまだはっきりしていない。
The policy is not yet definite.