Foreign Office abandoning overseas rule (5)
I believe the answer is:
reign
'rule' is the definition.
(I know that rule can be written as reign)
'foreign office abandoning overseas' is the wordplay.
'foreign office' becomes 'FO' (abbreviation).
'abandoning' is a deletion indicator.
'overseas' becomes 'foreign' (similar in meaning).
'foreign' with 'fo' taken away is 'REIGN'.
(Other definitions for reign that I've seen before include "Wield the sceptre" , "Rule as king or queen" , "Niger (anag)" , "Rule over in Niger" , "Hold sway, rule" .)