Around area a priest gathered mistletoe for one (8)
I believe the answer is:
parasite
'mistletoe for one' is the definition.
(mistletoe is a kind of parasite)
'around area a priest gathered' is the wordplay.
'around' indicates putting letters inside.
'area' becomes 'a' (maths abbreviation).
'gathered' indicates anagramming the letters.
'a'+'priest'='apriest'
'apriest' anagrammed gives 'parsite'.
'a' put inside 'parsite' is 'PARASITE'.
(Other definitions for parasite that I've seen before include "Animal that feeds off another" , "Say mistletoe" , "Organism that lives on another" , "Relies on host to survive" , "one who thrives on (or off) another" .)