Below zero in America after end of snowstorm (5)
I believe the answer is:
minus
'below zero' is the definition.
(I've seen this before)
'in america after end of snowstorm' is the wordplay.
'america' becomes 'us' (abbreviation for the United States).
'after' says to put letters next to each other.
'end of' indicates one should take the final letters.
The final letter of 'snowstorm' is 'm'.
'in'+'us'='inus'
'inus' after 'm' is 'MINUS'.
(Other definitions for minus that I've seen before include "Take-away (sign)" , "Reduced by the subtraction of - thus?" , "Lacking; below zero" , "Negative sign - negative thing" , "Less, without" .)