Fan of one of Europe's currencies almost pocketed each (6)
I believe the answer is:
zealot
'fan' is the definition.
(thesaurus)
'one of europe's currencies almost pocketed each' is the wordplay.
'one of europe's currencies' becomes 'zloty' (currency of Poland).
'almost' means to remove the last letter (most of the word but not all of it).
'pocketed' means one lot of letters goes inside another (pocket can mean to steal or take).
'each' becomes 'ea'.
'zloty' with its last letter removed is 'zlot'.
'zlot' enclosing 'ea' is 'ZEALOT'.
'of' acts as a link.
(Other definitions for zealot that I've seen before include "Fervent enthusiast" , "Radical" , "Fanatic or extreme enthusiast" , "Fervent, even militant, proponent of something" , "Single-minded supporter of a cause" .)