in a sense; in some way; to an extent
Used to qualify a statement, acknowledging that it is true from a certain perspective or to a degree, but not absolutely.
In a sense, what he says is correct.
This job is enjoyable in some ways.
ある意味で is the fuller adverbial form 'in a sense', while ある意味 is the shorter, more casual version often used the same way in conversation.
Phrase composed of ある (a certain) + 意味 (meaning).