Decade passed in relationships (8)
I believe the answer is:
twenties
'decade' is the definition.
(twenties is a kind of decade)
'passed in relationships' is the wordplay.
'passed' becomes 'went' (I've seen this in other clues).
'in' is an insertion indicator.
'relationships' becomes 'ties' (tie is a kind of relationship).
'went' put inside 'ties' is 'TWENTIES'.
(Other definitions for twenties that I've seen before include "what lies ahead for 27 [TEENAGER]?" , "Scores" , "ten years" , "The decade was said to be roaring" , "decade of frivolity" .)