Tires of terrible decade (7)
I believe the answer is:
forties
'decade' is the definition.
(forties is a kind of decade)
'tires of terrible' is the wordplay.
'terrible' indicates an anagram.
'tires'+'of'='tiresof'
'tiresof' with letters rearranged gives 'FORTIES'.
(Other definitions for forties that I've seen before include "British shipping forecast area" , "The age" , "See 25 Across" .)