Month in America, or less (5)
I believe the answer is:
minus
'less' is the definition.
(both can mean take away)
'month in america' is the wordplay.
'month' becomes 'M' (standard abbreviation).
'america' becomes 'US' (United States).
'm'+'in'+'us'='MINUS'
'or' acts as a link.
(Other definitions for minus that I've seen before include "(Of temperature) below zero" , "Less, without" , "Disadvantage" , "Negative sign - negative thing" , "Reduced by the subtraction of - thus?" .)