This is the 11443rd most frequent Russian word.
доверенным
"Trusted" or "confided."
In this sentence, 'доверенным' serves as an adjective describing the noun 'лицом' (representative), it is in the instrumental case as part of a predicate.
Он стал доверенным лицом моего друга.
He became my friend's trusted representative.
Here, 'доверенной' is an adjective modifying the noun 'особы' (person), in the genitive case, indicating possessive or attributive quality.
Ей дали статус доверенной особы в компании.
She was given the status of a trusted person in the company.
'Доверенными' functions as an adjective in this sentence, describing 'коллегами' (colleagues), in plural instrumental case, denoting who the subject interacts with based on the quality described.