Smiley's nemesis ousting large character from overseas port (7)
I believe the answer is:
karachi
'overseas port' is the definition.
'karachi' can be an answer for 'port' (I have seen 'Pakistani port ' mean 'karachi' so perhaps 'port' could also mean 'karachi'). I am unsure of the 'overseas' bit.
'smiley's nemesis ousting large character' is the wordplay.
'smiley's nemesis' becomes 'karla' (I've seen this in another clue).
'ousting' suggests deleting specific letters.
'large' becomes 'L' (eg in clothes sizes).
'character' becomes 'chi' (chi is a kind of letter of the alphabet).
'karla' with 'l' removed is 'kara'.
'kara'+'chi'='KARACHI'
'from' is the link.
Can you help me to learn more?
(Other definitions for karachi that I've seen before include "Pakistan's most populous city" , "City/port of Pakistan" , "Pakistani port" , "Pakistani metropolis" , "Capital of Pakistan, 1947-59" .)