Arduous searches (6)
I believe the answer is:
'arduous searches' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for quests that I've seen before include "Knightly searches" , "Pilgrimages or searches" , "Searches and odysseys" , "Chivalric searches" , "Long or arduous searches for something" .)