Foreign agents out: Resistance in (7)
I believe the answer is:
strange
'foreign' is the definition.
(I know that foreign can be written as strange)
'agents out resistance in' is the wordplay.
'out' is an anagram indicator (out can mean wrong or inaccurate).
'resistance' becomes 'r' (electronics abbreviation).
'in' means one lot of letters goes inside another.
'agents' with letters rearranged gives 'stange'.
'stange' going around 'r' is 'STRANGE'.
(Other definitions for strange that I've seen before include "Funny" , "Queer" , "Foreign" , "Irregular" , "Odd or unknown" .)