Take for granted part of the overseas sum earned (6)
I believe the answer is:
assume
'take for granted' is the definition.
(I've seen this in another clue)
'part of the overseas sum earned' is the wordplay.
'part of' indicates the answer is hidden within the clue.
'ASSUME' is hidden within 'overseas sum earned'.
(Other definitions for assume that I've seen before include "Take on, affect" , "Suppose - appropriate - feign - adopt" , "Suppose; put on" , "Take for granted, suppose" , "Guess" .)