Mistimed run for start of spring? It’s ludicrous (12)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

We think this is: an anagram (‘mistimed’) of RUN replacing ‘s’ (first letter or ‘start’ of spring) in s EASONABLE (‘start of spring?’) but ‘start of spring’ is doing double duty – any other thoughts out there?