Someone very like a campanologist (6)
I believe the answer is:
ringer
'campanologist' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for ringer that I've seen before include "clanger?" , "One is almost identical to another in the belfry" , "bell" , "Campanologist - spitting image" , "Campanologist - if dead, double" .)