A year in decline until now (2,3)
I believe the answer is:
as yet
'until now' is the definition.
(as yet means up to the current point)
'a year in decline' is the wordplay.
'year' becomes 'y'.
'in' indicates putting letters inside.
'decline' becomes 'set' (as in the sun setting).
'y' put within 'set' is 'syet'.
'a'+'syet'='AS YET'
(Other definitions for as yet that I've seen before include "Up to this point in time" , "Thus far" , "Up till now" .)