Surrounded foe finally in defeat (5)
I believe the answer is:
beset
'surrounded' is the definition.
(I've seen this before)
'foe finally in defeat' is the wordplay.
'foe finally' becomes 'e' (I can't explain this - if you can you should believe this answer much more).
'in' indicates putting letters inside.
'defeat' becomes 'best' (besting is a kind of defeating).
'e' placed into 'best' is 'BESET'.
Can you help me to learn more?
(Other definitions for beset that I've seen before include "surrounded by hostile forces" , "Beleaguer" , "besieged" , "dog" , "Surround (with problems)" .)