Reserve normal in the south-east (5)
I believe the answer is:
spare
'reserve' is the definition.
(synonyms)
'normal in the south-east' is the wordplay.
'normal' becomes 'par' (I've seen this in another clue).
'in the' means one lot of letters goes inside another.
'south east' becomes 'SE' (abbreviation).
'par' inserted within 'se' is 'SPARE'.
(Other definitions for spare that I've seen before include "With no excess fat" , "Refrain from using" , "Not required" , "Thin; surplus" , "Superfluous" .)