dyed-in-the-wool fan

Translations
преданный фанат
He's a dyed-in-the-wool fan of the band and follows them on every tour.
Он преданный фанат группы и следует за ними на каждом турне.
Definitions
A person who is extremely loyal and enthusiastic about something, such as a sports team or a band, and whose support or beliefs are unlikely to change.
Words
dyed

adjective
закоренелый
in

preposition
в
the

article or possessive pronoun
wool

noun
шерсть
fan

noun
поклонник