It's ten, we suspect, for a decade (8)
I believe the answer is:
twenties
'a decade' is the definition.
(twenties is a kind of decade)
'it's ten we suspect' is the wordplay.
'suspect' is an anagram indicator.
'its'+'ten'+'we'='itstenwe'
'itstenwe' is an anagram of 'TWENTIES'.
'for' acts as a link.
(Other definitions for twenties that I've seen before include "what lies ahead for 27 [TEENAGER]?" , "They were roaring in the last century" , "decade of frivolity" , "The decade was said to be roaring" , "First adult years" .)