Admirer of a party with rightwing extremist radical leaders (6)
I believe the answer is:
adorer
'admirer' is the definition.
(synonyms)
'a party with rightwing extremist radical leaders' is the wordplay.
'party' becomes 'do' (do is a kind of party).
'with' says to put letters next to each other.
'leaders' says to take the initial letters.
The first letters of 'rightwing extremist radical' is 'rer'.
'a'+'do'+'rer'='ADORER'
'of' is the link.
(Other definitions for adorer that I've seen before include "Lover; worshipper" , "someone in love" , "One loves" , "Someone who loves greatly" , "One would love" .)