Always succeeded in case of rare defeat (7)
I believe the answer is:
reverse
'defeat' is the definition.
(I've seen this before)
'always succeeded in case of rare' is the wordplay.
'always' becomes 'ever' ('ever' can be a synonym of 'always').
'succeeded' becomes 's' (genealogical abbreviation).
'in' indicates putting letters inside.
'case of' says to hollow out the word (remove centre letters) (outsides of).
'rare' with its middle taken out is 're'.
'ever'+'s'='evers'
'evers' going into 're' is 'REVERSE'.
(Other definitions for reverse that I've seen before include "Back (of a coin or medal)" , "Transpose" , "Invert" , "Turn inside out or upside down" , "Backtrack" .)