Old rocker suffering setback longed to be alone (8)
I believe the answer is:
detached
'be alone' is the definition.
(thesaurus)
'old rocker suffering setback longed' is the wordplay.
'old rocker' becomes 'ted'.
'suffering setback' shows that the letters should be reversed in order.
'longed' becomes 'ached' ('ache' can be a synonym of 'long').
'ted' backwards is 'det'.
'det'+'ached'='DETACHED'
'to' is the link.
(Other definitions for detached that I've seen before include "free of ties" , "Separate, disconnected" , "Type of house" , "Separated from - maybe a house" , "Clinical" .)