Line sauna roughly and make like winter? (9)

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

An anagram (‘roughly’) of ‘line sauna’, with a rather odd definition: to annualise is to express e.g. an interest rate as it would be for a whole year; I suppose the idea here is that if you ‘make like winter’, you are encompassing a calendar year.