Supplementary (5)
There are a few possibilities for this:
additional
'supplementary' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for extra that I've seen before include "walk-on part" , "Studio crowd player" , "An additional thing" , "special edition of the paper" , "Bonus; surplus" .)
'supplementary' is the definition.
(similar in meaning)
This is the entire clue.
(Other definitions for added that I've seen before include "Counted up" , "Said" , "Totted" , "Appended; totalled" , "Summed up" .)
'supplementary' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for additional that I've seen before include "Extra" , "with sums, perhaps" .)