Surplus to requirements (5)
'surplus to requirements' is the definition.
(extra can mean spare or unneeded)
This is the entire clue.
(Other definitions for extra that I've seen before include "Possibly overthrow" , "late edition" , "Cricket run; unusually" , "Minor person screened" , "spotted at rear of the platoon?" .)
'surplus to requirements' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for spare that I've seen before include "Excess to requirements" , "Thin; left over" , "Thin; surplus" , "slit at top of trousers in Scotland" , "A feature of trousers" .)