Queen to marry in this decade? (8)
I believe the answer is:
thirties
'decade?' is the definition.
(thirties is a kind of decade)
'queen to marry in this' is the wordplay.
'queen' becomes 'r' (r is abbreviation regina. e.g. in ER ).
'to marry' becomes 'tie' ('tie' can be a synonym of 'marry').
'in' is an insertion indicator.
'r'+'tie'='rtie'
'rtie' inserted within 'this' is 'THIRTIES'.
(Other definitions for thirties that I've seen before include "US Depression era, the ''hungry ... ''" , "Nineteen thirty to nineteen thirty nine" , "The decade described as hungry." .)