Not amateur side dropping American for now (3,3)
I believe the answer is:
pro tem
'for now' is the definition.
(short for pro tempore, meaning for the time being)
'not amateur side dropping american' is the wordplay.
'not amateur' becomes 'pro' (I've seen this before).
'side' becomes 'team' (a side is a sporting team).
'dropping' is a deletion indicator.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'team' with 'a' taken away is 'tem'.
'pro'+'tem'='PRO TEM'
(Other definitions for pro tem that I've seen before include "'For the time being (3,3)'" , "not indefinitely extended" , "For the time being (Latin abbreviation)" , "For the present" , "Informally, for the time being" .)