Coldest season (6)
I believe the answer is:
winter
'coldest season' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for winter that I've seen before include "'If . . . . . . comes, can spring be far behind?'" , "period of freeze?" , "Cold season" , "Cold period" , "'Now is the . . . . . . of our discontent' (Richard III)" .)