The most common and most likely answer to this crossword clue is the 4 plus 10 letter word HERO WORSHIPPER
I've seen this crossword clue in The Daily Telegraph
H
E
R
O
W
O
R
S
H
I
P
P
E
R
Buddy explains!
The straight part
We know that "One who idolises" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one who idolises = hero worshipper.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.