Compare white American coming in with sweetheart (7)
I believe the answer is:
balance
'compare' is the definition.
(thesaurus)
'white american coming in with sweetheart' is the wordplay.
'white' becomes 'blanc' (I've seen this before).
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'coming in' indicates putting letters inside.
'with' says to put letters next to each other.
'sweetheart' becomes 'e' (the heart/centre of 'sweet').
'blanc' going around 'a' is 'balanc'.
'balanc'+'e'='BALANCE'
(Other definitions for balance that I've seen before include "Libra - amount in account" , "Surplus" , "emotional stability" , "Poise" , "A steady position as on scales" .)