Solo item turned out to be arduous (8)
I believe the answer is:
toilsome
'be arduous' is the definition.
('toilsome' can be a synonym of 'arduous')
'solo item turned out' is the wordplay.
'turned out' is an anagram indicator.
'solo'+'item'='soloitem'
'soloitem' with letters rearranged gives 'TOILSOME'.
'to' is the link.
(Other definitions for toilsome that I've seen before include "needing much work" , "laborious" , "Needing much effort" .)